Media servowriting system

ABSTRACT

A system and methods for efficiently performing media writing functions is disclosed. The system and methods include: detecting media movement with respect to a base and heads during reading and writing, and moving the heads in response; using an interferometer, such as a dual beam differential interferometer, to dynamically monitor disk position and address perceived errors; and minimizing repeatable and non repeatable runout error by writing data, such as servo bursts, in multiple revolutions to average adverse runout conditions. The present system has the ability to use an interferometer to enhance media certification and perform on line, in situ monitoring of the media, and includes shrouding, head mounting, disk biasing, and related mechanical aspects beneficial to media writing.

[0001] This application claims the benefit of U.S. Provisional PatentApplication Serial No. 60/367,046, filed Mar. 23, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the field of datastorage media, and more specifically to systems and methods forefficiently initializing, certifying or otherwise reading data from orwriting data to such media.

[0004] 2. Description of the Related Art

[0005] Disk drives are magnetic recording devices used for the storageof digital information. The digital information is recorded onsubstantially-concentric tracks on either surface of one or moremagnetic recording disks. The disks are rotatably mounted on a spindlemotor, and information is accessed by read/write heads mounted toactuator arms rotated by a voice coil motor. The voice coil motorrotates the pivoting arms and moves the heads radially over the surfaceof the disk or disks. During servowriting and/or initialization of adisk, the read/write heads must generally be accurately positioned onthe disk to ensure proper reading and writing of servo information thatwill define the data storage tracks. After the servo writer writes theservo patterns on the disks, the control system is added to the harddrive assembly.

[0006] Movement of the pivoting arms is controlled by a servo system,which utilizes servo information recorded on one or more of the disks tocenter the head on a particular track. Servo information is utilized todetermine an actual position of the heads. A voice coil motor (VCM)moves the heads if the actual head position deviates from a desired headlocation. Head position is typically controlled by a closed loop servosystem.

[0007] The servo information in the servo tracks is often written withtiming derived from a master clock track in the servo writing system.Writing of servo information must be precise. Servo information istypically recorded by special instruments containing precise mechanicalpositioners, positioned using highly accurate feedback devices such asoptical encoders or laser interferometers.

[0008] A media servowriter is a device dedicated primarily to the servodata writing function. It can also perform other functions related tohard disk preparation for insertion into a hard disk drive. Inoperation, a media servowriter writes multiple disks in preparation fortheir placement in an HDD, with the goal being minimal further diskpreparation once each disk is located in the HDD. Media servowriters canthus be housed in one location while hard disk assembly includingcompleted disks may be performed at another location with the knowledgethat the servowritten disks have been tested and approved for certainparameters.

[0009] Previously available servowriters suffer from a variety ofshortcomings and system performance issues. An example of known systemperformance issues is that of system positioning accuracy: positioningheads over tracks to accurately read and write information at highspeeds is an ongoing performance consideration that can always beimproved or enhanced. Most, if not all, of the previously availablesystems suffer from an inability to support custom read/write heads, orprovide accurate micro-move and settle times or track holding accuracy.

[0010] One particular problem with currently available disk drives andservowriters is the complexity associated with knowing the location of ahead over a disk, and detecting and utilizing relative movements ofdisks, positioners, heads, and related equipment with respect to areference point or plane. In current servowriters, no action occursduring normal operation to track or control disk or spindle positionwith respect to the drive base. Instead, the system tracks and controlshead position with respect to some servowriter structural referencepoint, with the implicit assumption that disk position is sufficientlywell known and stationary. In actual operation, however, the disks andspindle may shift, vibrate, deform, or otherwise alter their position inspace with respect to the structural reference point. Current systems donot physically track disk position nor compensate for movement orirregularities resulting from real world conditions, including theaforementioned conditions and non-repeatable run out movement. Aservowriter without the ability to track disk position and compensatefor positional or movement irregularities may introduce or otherwisesuffer from errors while heads are reading from or writing to the disks.This error introduction may limit the spin rate and/or track density ofthe disks.

[0011] It would be beneficial if one could track and compensate formedia movement during the read and write process, thereby decreasing therisk of reading from or writing to incorrect locations on the mediasurface.

[0012] Another problem with currently available disk drives andservowriters is that of accurate head positioning. During the process ofwriting servo tracks on magnetic media, servo patterns must bepositioned with high accuracy on different radial tracks. Thetraditional method of locating servo patterns on disks is to use aread/write head flying over a spinning media disk. The read/write headis attached to a rotary positioning device comprising a voice coil,associated voice coil motor, and a rotary optical encoder for closedloop positioning purposes. The rotary positioning device is used to holdthe read/write head and swing the head over the spinning media disk.Errors in servo track accuracy can occur whenever the system does notmaintain head position in a controlled radius as the media disk spinsbelow the head. In certain circumstances the axis of the spinning mediadisk can translate laterally in the plane of rotation or the axis canwobble, tilting about a pivot point not coincidence with the media diskplane, thereby also translating the disk with respect to the head. Headposition errors may also occur if the entire optical encoder fails toprecisely track head position. The entire positioning device cantranslate or vibrate with respect to the spinning disk, or flexing ofany components connecting the head to the optical encoder can producepositional errors.

[0013] Previous systems have employed a rigid mechanical connectionbetween the optical encoder and the heads as well as a stable mechanicalreference between the optical encoder and the axis of the spinning disk.In a disk having a track pitch below one micron, the rigid positionallinkage performance between the optical encoder and the head as well asthe optical encoder and spindle axis can be compromised by variousfactors, such as wobble or translation of the spindle axis within itsbearing mount, causing radial runout. Other potentially problematicfactors may include tiny distortions of the shape of any hardware thatmechanically references the head to the spindle axis. Externalvibrations, vibrations from the spindle motor, temperature fluctuationsor flutter from the disk can all contribute nanometer fluctuations anderrors in positioning the head at constant track radius.

[0014] It would be beneficial to have a servo system that minimizes thedependence on the idealized mechanical references connecting spindleaxis position to head position, thereby minimizing errors andfluctuations in the radius of servo data, or marks.

[0015] Another example of known system performance issues is that ofsystem positioning accuracy: positioning heads over tracks to accuratelyread and write information at high speeds is an ongoing performanceconsideration that can always be improved or enhanced. One particularproblem with currently available servowriters is the equipment used toformat a disk writes a set of servo sectors to the disk, and thepresence of relatively significant servo sector errors can cause theservowriter to indicate the disk is bad during verification testing.Alternately, when writing to a formatted disk, the presence ofrelatively significant errors in the servo sectors causes the disk driveto mark those sectors as unusable for data storage, either by detectingexcessive servo errors while track following or excessive errorsdetected during data writing and reading, with the result that the datastorage capacity of the disk would be reduced. Thus the downside of theold method of writing servo sectors or data sectors and monitoring thewritten data for errors would be discarded disks or unusable disk area.These drawbacks decrease yield and reduce available storage capacity.

[0016] It would be beneficial to have a method of writing data,including servo data, that would reduce the risk of decreased yieldsand/or storage capacity of hard disks as compared with previously knownsystems.

[0017] Furthermore, most, if not all, of the previously availablesystems suffer from an inability to support custom read/write heads, orprovide accurate micro-move and settle times or track holding accuracy.

[0018] Disk drive heads are replaced periodically due to wear and tear.Instead of staking, wherein the head suspension and the head mount tab3501 may suffer permanent deformation, it would be beneficial to offer adesign that does not encounter permanent mechanical deformation duringassembly or reassembly. In a particular hardware implementation, stakinghas required mounting a tab replacement or head arm or E-block afteronly two or three head replacements due to permanent deformation of theboss receiving bore of the head mount. It would be preferable to offer adesign that can impart less distortion to the interface between the HGAand the mating head mount bore, increasing the number of reuses of thehead mount tab before replacement is indicated.

[0019] Further, hard disk drives rely heavily on position referenceinformation “written” or recorded as concentric bands of tracks ontodisk surfaces. The operation of creating those tracks, known as servotrack writing, requires precise record-phase head positioning andspindle mechanisms, as well as accurate timing and control electronics.The servo track writing process traditionally has been performed afterdisks have been installed into a “hard disk assembly”, or HDA. At thestage where disks are located in an HDA, the disks have been positionedon a spindle within the HDA. The HDA read-write heads have been loadedonto the disk or disks. An operator has traditionally placed the HDAonto a Servo Track Writer device that provides head positioning andservo pattern information to the HDA to enable proper recording of theservo tracks onto the disk or disks. This traditional technique isespecially useful when multiple disks are used within the HDA.

[0020] However, as disk areal data density has increased, many Hard DiskDrives today utilize only one disk, decreasing the usefulness of theaforementioned technique. Further, increased areal data density isfrequently accompanied by an increase in track density, which requiresthat the HDA write additional servo tracks. With at least two servotracks for every data track, the number of servo tracks has increased attwice the rate of data tracks for a disk of fixed size or area. Thisincreased number of tracks results in a dramatic increase in the timerequired to write the servo tracks. Servo writing, which previously tooka few minutes can now easily exceed a half hour or more, depending onSTW machine parameters, disk size, rotational speed (RPM), and totalnumber of servo tracks. This time increase, coupled with the fact thatmany disk drives today use only a single disk, has created a demand fora media track writer, or MTW, that can simultaneously record servotracks on multiple disks prior to installation into an HDA.

[0021] One aspect of the MTW that is particularly noteworthy is themechanical clearance between the disk inside diameter, and the hub orchuck outside diameter, namely the disk opening and the hub that fillsthe opening. A significant clearance dimension is necessary to enablefast and reliable disk installation on and off the hub and toaccommodate disk and hub manufacturing tolerances. If this clearance istoo large, the disk or disks will move laterally and possibly axiallyduring high RPM rotation. A finite clearance value exists under any setof dimensions. This clearance, if not addressed in some manner, createsan uncertainty with regard to the concentricity of servo tracks to diskID, and can in certain circumstances result in significant eccentricityerrors introduced when removing disks from the MTW and installed into adisk drive HAD. If uncontrolled, these errors can in certaincircumstances exceed 4000 microinches, or millionths of an inch.Excessive eccentricity, or servo track “runout”, can cause servo captureand performance problems for the HDD, in that the head can be mislocatedabove the disk and can run outside a track, or begin in one track andend in another.

[0022] An additional aspect of a media servowriter is holding a hub,specifically a hub of a disk stacking cylinder employed to hold multipledisks during disk servowriting and certification. Previously availablehub holding devices used some type of mechanical “jaws” that gripped theexterior of the hub and/or the notch formed between the hub and the maincylinder. The jaws were formed of some type of metal and were metalpieces used to pin the hub down and hold it in position by applyingpressure to the upper side of the hub. These jaw-type locking devicestend to be imprecise in holding the hub or other cylindrical piece. Atsignificantly high RPMs, such as in excess of 10,000 to 20,000 RPMs,centrifugal force works to pry these devices open, and many jaw typedevices are pried open or move the piece as a result of high forcesapplied thereto. This prying tends to damage the hub and/or maintainingdevice and is generally unacceptable. Thus the previous devices could becharacterized as easily pried open, with poor repeatability, and highlysubject to movement of the piece.

[0023] It would be beneficial to provide a system overcoming thesedrawbacks present in previously known systems and provide an improvedmedia servowriter, disk writer, and/or other device having improvedfunctionality over devices exhibiting those negative aspects describedherein.

SUMMARY OF THE INVENTION

[0024] According to one aspect of the present design, there is provideda method for tracking and controlling media read/write characteristics.The method comprises creating media having a predetermined expectedbaseline configuration, reading the media having the predeterminedexpected baseline configuration, determining whether the media has movedfrom an expected position based on the media reading of thepredetermined expected baseline condition, and correcting data hardwarebased on determining whether the media has moved from the expectedposition.

[0025] According to a second aspect of the present design, there isprovided a method for minimizing likelihood of a head within aservowriting apparatus contacting a disk located therein. The methodcomprises sensing sound intensity in a predetermined frequency rangefrom a first sensor positioned at a first location within theservowriting apparatus, determining the existence of a pending headcrash based on the sound intensity; and moving an element of theservowriting apparatus upon determining the existence of the pendinghead crash.

[0026] According to a third aspect of the present design, there isprovided an apparatus for controlling airflow over rotating media. Theapparatus comprises at least one baffle covering the media, the at leastone baffle comprising at least one cavity shielding at least a portionof the rotating media; wherein the at least one baffle provides theability to inhibit turbulent flow when the rotating media rotates.

[0027] According to a fourth aspect of the present design, there isprovided a method for changing a head assembly employed in a mediawriting device. The method comprises providing a head mount assemblyhaving a bore passing therethrough, positioning the head assemblyadjacent the head mount, aligning the head assembly with the head mount,and press fitting the head assembly to the head mount.

[0028] According to a fifth aspect of the present design, there isprovided a system for detecting movement of a plurality of disks mountedto a spindle. The system comprises a transmitter/receiver capable ofemitting a first beam of energy toward the spindle and receiving energyfrom the spindle and an error calculator determining differences betweenactual head position based on the reflective element position andorientation of the spindle.

[0029] According to a sixth aspect of the present design, there isprovided a system for positioning a head over a disk, the disk mountedto a spindle. The system comprises a transmitter/receiver capable ofemitting a first beam of energy toward the spindle and receiving energyfrom the spindle, a reflective element positionally emulating the headand oriented to receive a second beam of light energy from thetransmitter/receiver and reflect the second beam back toward thetransmitter/receiver, and an error calculator determining differencesbetween actual head position based on the reflective element positionand orientation of the spindle.

[0030] According to a seventh aspect of the present design, there isprovided a system for accurately positioning a head over rotating media,the rotating media able to spin about a center axis. The systemcomprises an interferometer having the ability to emit light energy andmeasure an effective distance between the head and the spindle, andmeans for computing a correction factor to be applied to the spindle tocorrect for any perceived distance errors related to the headmeasurement.

[0031] According to an eighth aspect of the present design, there isprovided a system for determining spindle orientation inaccuracies. Thesystem comprises an interferometer having the ability to emit lightenergy and measure an effective distance between the interferometer andthe spindle, and means for computing a correction factor for applicationto the spindle to correct for perceived errors.

[0032] According to a ninth aspect of the present design, there isprovided a method for increasing magnetic disk yield during themanufacturing process. The method comprises initially writing a firstcomplete set of servo data to a magnetic disk, subsequently writing atleast one additional set of servo data to the magnetic disk, evaluatingthe quality of the servo data written, and removing the lowest qualityservo data and retaining the highest quality servo data.

[0033] According to a tenth aspect of the present design, there isprovided a method of assessing track writing performance on a media. Themethod comprises monitoring spindle axis position with respect to areference position, and providing the spindle axis position with respectto a reference position to a processor.

[0034] According to an eleventh aspect of the present design, there isprovided a method of computing a media track writing performance metric.The method comprises at least one from the group including computing astandard deviation of an observed track write radius from a desiredtrack write radius and decomposing the standard deviation intorepeatable and nonrepeatable components, computing time dependent servomark positions, and computing optically inferred spindle axis positions.

[0035] According to a twelfth aspect of the present design, there isprovided a method of computing a performance metric for media trackwriting. The method comprises monitoring position of a rotatingcomponent of a holder maintaining the media, computing a topologicalradius of a surface of the rotating component, and determining adifference between the rotating component position and the topologicalradius, wherein the difference equals rotating component wobble.

[0036] According to a thirteenth aspect of the present design, there isprovided a method for biasing at least one disk fixedly attached to aspindle. The method comprises applying a biasing lateral force to afirst disk fixedly attached to the spindle thereby tightly interfacingthe disk with the spindle at one portion of the disk and applying adifferently oriented biasing lateral force to any second disk fixedlyattached to the spindle.

[0037] According to a fourteenth aspect of the present design, there isprovided a method for biasing a disk attached to a spindle, comprisingapplying a biasing lateral force to the disk fixedly attached to thespindle thereby tightly interfacing the disk with the spindle at oneportion of the disk.

[0038] According to a fifteenth aspect of the present design, there isprovided a system for maintaining media, comprising a cap, at least onespring holding the cap, and a fluid release ball bearing arrangementhaving the ability to slidably engage and release the cap using forcegenerated by the at least one spring.

[0039] According to a sixteenth aspect of the present design, there isprovided a device for holding a rotating hub, comprising a chuck clamphousing, a mounting plate fixedly mounted to the chuck clamp housing, aspindle within the chuck mounting plate, and a chuck clamp surroundingthe chuck mounting plate and having the ability to engage the hub,wherein the chuck clamp comprises a plurality of finger elements.

[0040] These and other objects and advantages of the present inventionwill become apparent to those skilled in the art from the followingdetailed description of the invention and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a general conceptual representation of the servowritingsystem according to one aspect of the current invention;

[0042]FIG. 2 represents the mechanics of the servo writing device of oneaspect of the current invention;

[0043]FIG. 3 is the multiple disk and spindle arrangement used inaccordance with one aspect of the current invention;

[0044]FIG. 4 presents a single multiple read/write head positionerarrangement that may be utilized in accordance with one aspect of thecurrent invention;

[0045]FIG. 5 presents an alternate view of the servowriting device withmedia cover and in-place positioner according to one aspect of thecurrent invention;

[0046]FIG. 6 is a conceptual view of the optical inspection systemaccording to one aspect of the current invention;

[0047]FIG. 7 shows ideal operation of writing bursts to a track;

[0048]FIG. 8 illustrates a more typical operation of burst writingobserved under certain typical conditions;

[0049]FIG. 9 shows a conceptual illustration of the sinusoidal dipulsewriting of a burst;

[0050]FIG. 10 presents multiple dipulse writing over multiple passes inaccordance with an aspect of the present invention;

[0051]FIG. 11 represents one aspect of the inventive device disclosedherein;

[0052]FIG. 12 represents the relationship between a single data sectorand an associated servo sector;

[0053]FIG. 13 shows the disposition of servo sectors at substantiallyregular angular offset positions around the disk according to one aspectof the current invention;

[0054]FIG. 14 is a schematic cross-sectional view at some point alongthe length of a fiber optical tri-coupler such as used in aninterferometer according to one aspect of the current invention;

[0055]FIG. 15 is a schematic of an embodiment of an interferometeraccording to the present invention;

[0056]FIG. 16 is a schematic of an alternate embodiment of aninterferometer according to the present invention;

[0057]FIG. 17 is a graph showing the output signals from photodetectorson the interferometer versus the input phase-difference between theinput beams according to one aspect of the current invention;

[0058]FIG. 18 represents a conceptual top view of an acoustic sensorimplemented in one aspect of the present invention;

[0059]FIG. 19 illustrates a perspective view of the left baffle shroudaccording to one aspect of the present invention;

[0060]FIG. 20 is a perspective view of an eleven-shroud right baffleaccording to one aspect of the present invention;

[0061]FIG. 21 represents the hardware associated with the servo writingdevice according to one aspect of the current invention;

[0062]FIG. 22 is a top cutaway view of the left baffle shroud accordingto one aspect of the current invention;

[0063]FIG. 23 presents a side cutaway view of the left baffle shroudaccording to one aspect of the current invention;

[0064]FIG. 24 shows a bottom view of the left baffle shroud according toone aspect of the current invention;

[0065]FIG. 25 illustrates a side view of the right baffle shroudaccording to one aspect of the current invention;

[0066]FIG. 26 is an alternate perspective view of the right baffleshroud according to one aspect of the current invention;

[0067]FIG. 27 shows a bottom view of the right baffle shroud accordingto one aspect of the current invention;

[0068]FIG. 28 is a perspective view of the clock shroud according toanother aspect of the current invention;

[0069]FIG. 29 presents a top view of the clock shroud of FIG. 28according to one aspect of the current invention;

[0070]FIG. 30 is a rotary voice coil motor design according to oneembodiment of the current invention;

[0071]FIG. 31 presents a coil housing according to one embodiment of thecurrent invention;

[0072]FIG. 32 presents a front and side view of a coil according to oneembodiment of the current invention;

[0073]FIG. 33 shows a scale holder and shaft used to maintain and rotatethe positioner, E-block, and related components according to oneembodiment of the current invention;

[0074]FIG. 34 shows the E-block assembly, including a plurality of headsattached thereto on head assemblies according to one embodiment of thecurrent invention;

[0075]FIG. 35 shows an example of a mounting tab that may be mounted tothe E-block and that may operate in accordance with the presentinvention according to one embodiment of the current invention;

[0076]FIG. 36 shows a top view of the E-Block bifurcated by a centerlineand particularly highlighting the slots for receiving the dowels or pinsof the mounting tab according to one embodiment of the currentinvention;

[0077]FIG. 37 is an exploded view of one aspect of an assembly tool thatmay be used in accordance with the present invention;

[0078]FIG. 38A shows front and side views of one aspect of a leftsection of an assembly tool according to one embodiment of the currentinvention;

[0079]FIG. 38B illustrates front, rear, and side views of one aspect ofa center section of an assembly tool according to one embodiment of thecurrent invention;

[0080]FIG. 38C represents front and side views of one aspect of a rightsection of an assembly tool according to one embodiment of the currentinvention;

[0081]FIG. 39 shows various components that may be employed in theinventive press fit method disclosed herein according to one embodimentof the current invention;

[0082]FIG. 40 shows one detailed aspect of a head assembly according toone embodiment of the current invention;

[0083]FIG. 41 is a view of an assembly tool maintaining a mounting taband head assembly prior to press fitting with an alignment pin insertedtherethrough according to one embodiment of the current invention;

[0084]FIG. 42 illustrates an assembly tool maintaining a mounting taband head assembly prior to press fitting with a second alignment pininserted therethrough according to one embodiment of the currentinvention;

[0085]FIG. 43 shows an assembly tool maintaining a mounting tab and headassembly and press fitting the components together using a vise orclamping device according to one embodiment of the current invention;

[0086]FIG. 44 is an aspect of the locking cap arrangement of a systemaccording to one aspect of the current invention;

[0087]FIG. 45 is a close view of a locking cap according to an aspect ofthe present invention;

[0088]FIG. 46 is an aspect of the locking cap arrangement with bearingsreleased and in release position according to one embodiment of thecurrent invention;

[0089]FIG. 47 is a close view of the locking cap arrangement withbearings released and in release position according to one embodiment ofthe current invention;

[0090]FIG. 48 illustrates the finger gripping arrangement used to grip ahub holding one or more disks according to one embodiment of the currentinvention;

[0091]FIG. 49 is an alternate view of the finger gripping mechanismaccording to one embodiment of the current invention; and

[0092]FIG. 50 is another alternate view of the finger gripping mechanismaccording to one embodiment of the current invention.

DETAILED DESCRIPTION OF THE INVENTION

[0093] According to the present invention, there is provided an enhancedmedia servowriter having several aspects constituting improvements overpreviously known designs. An aspect of the present invention is a systemand method for tracking disk and spindle position, typically in amultiple media disk arrangement, whereby data from the disks or spindleare fed back to hardware and/or software to compensate for positionerrors during reading and/or writing to the media.

[0094] In a particular aspect of the present invention, a non-contactradiation detection system cooperates with an ideal disk produced usingpatterning technology to detect movement of disks mechanically coupledto a spindle. The system further utilizes an ideal magnetic disk todetect movement of disks mechanically coupled to a spindle. Further, thesystem and method disclosed herein detect spindle and disk (or disks)movement with respect to a common base by detecting radiation reflectedby a rotating part of the spindle.

[0095] A particular implementation measures and calculates the distancebetween the spindle axis position and an emulated head position and usesthis distance to more accurately position the head. The system mayemploy a dual channel interferometer, such as a multiphase or guidedwave interferometer, to reflect energy beams off the spindle holding therotating media by using a retro reflector emulating head position and alensing arrangement. The interferometer determines actual distance fromthe head to the spindle using the emulated head position and the systemutilizes a digital signal processor or other computing device to comparethat distance to any topological shift in the spindle position to findan overall error. The system then applies the overall error to the voicecoil to correct head position. Alternate aspects of the invention employinterferometers in the z (vertical) direction or in the y direction todetermine and compensate for tilt, vibration, or other undesirable mediaand/or head shifting.

[0096] In one aspect, the interferometer operates by reflecting lightoff the polished chuck holding the disks, which is part of the rotatingportion of the spindle and thus accurately emulates spindle axisposition and orientation. Due to errors in the spindle chuck (notperfectly cylindrical, tilted or otherwise computationally off desiredorientation) the system determines the topological offset of the chuckand uses this value in combination with the raw distance between thehead and the chuck and/or spindle to determine an overall positionalerror rate signal. The DSP processes this error signal to produce acorrective positional signal, which the DSP applies to the voice coil orother control device. The result is a compensation for angular tiltand/or shifts in orientation and/or the relationship between the head orthe media. The retro reflector may be a corner cube or cat's eye or anyother optical element having beneficial functionality in thisinterferometer-emulated head position arrangement.

[0097] The devices and methods disclosed herein may be employed inservowriting and/or data writing systems, and may be used in othersystems employing a device such as a head to write or read data to orfrom rotating media.

[0098] A further aspect of the present invention includes a method forincreasing the yield of magnetic disks during the manufacturing process.According to an aspect of the present invention, once the system haswritten the set of servo sectors to the disk, the servowriter verifiesdata written in the servo sectors to validate the disk. If the datawritten within the servo sectors exhibits sufficient integrity, theservowriting process is considered successful, and data sectorscorresponding to the servo sectors are produced and validated. The datasectors may store data subsequently written to the disk.

[0099] Another aspect of the invention utilizes the writing and readingconcepts disclosed above to increase the data storage capacity of a harddisk drive by writing multiple duplicate versions of data to the disk indifferent data sectors around the disk, and then retaining only the dataexhibiting a sufficient degree of integrity. In this aspect of theinvention, similar to the servowriting aspect outlined above, more thanone set of data sectors is written to the media disk during normaloperation, preferably during the same revolution. As a result, insteadof a single set of data sectors disposed at predetermined positionsaround the disk based on available space on the disk, this aspect of themethod disclosed herein produces one or more additional sets of datasectors, each of these data sectors being disposed at predeterminedpositions around the disk with respect to other data sectors. Oncewritten, the HDD determines the set of data having the highest dataintegrity by comparing all data sets against original or baseline data.The system may then erase lower quality or duplicate data.

[0100] A further aspect of the present invention is tracking disk andspindle position, typically in a multiple media disk arrangement,whereby data from the disks or spindle are fed back to hardware and/orsoftware to compensate for position errors during reading and/or writingto the media. This aspect of the invention may or may not be used withthe hardware disclosed. A non-contact radiation detection systemcooperates with an ideal disk produced using patterning technology todetect movement of disks mechanically coupled to a spindle. Anotheraspect of the present invention utilizes an ideal magnetic disk todetect movement of disks mechanically coupled to a spindle. An aspect ofthe invention provides a system and method for detecting spindle anddisk (or disks) movement with respect to a common base by detectingradiation reflected by a part of the spindle.

[0101] Media Servowriter

[0102]FIG. 1 is a general conceptual representation of the servowritingsystem in which the present invention may be employed. From FIG. 1, thesystem controller 102 controls clock pattern 103, robotics control 104,position servo 105, and PES and verify block 106. Robotics control 104,position servo 105, and PES and verify blocked 106 perform functionsrelated to the present invention. For example, robotics control 104provides commands to drive the motors and sensors interacting with thespindle and air bearing to drive the multidisk spindle and air bearingarrangement.

[0103] In one embodiment, clock pattern circuit 103 generates a clockingsignal and establishes the pattern generated on the disk surface. Systemcontroller 102 provides an indication to clock pattern circuit 103 toinitiate a pattern on the disk surface when appropriate, such as duringdisk processing routines when it is appropriate for certification andservowriting to occur. Pattern read/write block 107 provides signals forreading and writing the pattern established by the clock pattern circuit103. This pattern is the pattern used for this certification asdescribed herein, which is written to and read from the media. Clockpattern circuit 103 also issues commands for servo/clock writing toservo clock read/write circuit 108. Servo clock read/write circuit 109writes servo clock information to the disk and reads that clockinginformation to assess the validity of the servo data.Servo/certification module 110 determines the proper time, data, andpattern for servowriting for the multiple head/multiple disk arrangementof the present invention.

[0104] Operation of servo/certification module 110 in one embodiment isdescribed below. Servo certification module 110 receives data frompattern read/write block 107 and servo clock read/write circuit 108.Servo certification module 110 transmits appropriate data and receivesrelevant data at multiple data preamps 111 a through 111 n, where n isthe total number of preamps used to write to multiple disks. Forexample, but without limitation, a system may employ ten disks andtwenty heads in connection with four preamps. Uniform correspondence inpreamp to disk ratio between data preamps is not required, and one datapreamp may write to one disk while another may write to several mediadisks in the same configuration. Multiple data preamp and diskarrangements may be employed while still within the course and scope ofthe present invention. Servo clock read/write circuit 108 also transmitsand receives relevant data at clock preamp 112. These preamps filter andamplify data received from the various circuits and transmit theamplified signals to the appropriate read/write heads 113 a-n.

[0105] In association with one possible implementation of the presentinvention, media disks are located on spindle 120 and read/write heads113 a-n positioned proximate the disk surface using the head stackassembly. The spindle 120 preferably rides on an air bearing 122,thereby operating to rotate the disks in an efficient manner whilemultiple heads engage the media 121, such as multiple hard disks 121a-n, in order to read and write appropriate information. The systemwrites patterns, including servo patterns, to each disk using theread/write heads. As reading and writing using multiple heads mayinvolve simultaneous processing, reduced processing requirements andtime sharing could result in significant cost savings. The system writesservo data and performs certification in a timely and cost effectivemanner using the spindle 120 and head stack assembly arrangement.

[0106] Compensation for Head and Disk Movement

[0107] One aspect of the invention disclosed herein detects movement(other than spinning) of the spindle and/or media, such as computerdisks, with respect to a reference location, such as a granite base towhich disk drive or servowriter hardware is attached, or directly withrespect to a head interacting with the media. The present inventioncomprises methods and systems for compensating for such movement. Theresult of this aspect of the invention is to in most cases decrease therelative movement (other than spinning) between the heads and disksduring normal disk drive or servowriting operation.

[0108] Four aspects and various related embodiments of the currentinvention are specifically disclosed herein for detecting movement ofmedia disks and/or the spindle holding the media with respect to thebase. These four aspects compensate movement with respect to the baseand/or heads. The first aspect is a non-contact radiation detectionsystem combined with an ideal disk produced using patterning technology.The second aspect is an ideal magnetic disk serving as a reference for ahead reading information from the ideal magnetic disk. The third aspectis a non-contact radiation detection system that bounces radiation offone or more parts of the spindle. The fourth aspect is a non-contactradiation detection system that bounces radiation off both a part of thespindle and one or more parts of one or more heads.

[0109] 1. Non-Contact Radiation Detection System Combined with an IdealDisk Produced Using Patterning Technology

[0110] In a first aspect of the current invention, a non-contactradiation detection system cooperates with an ideal disk produced usingpatterning technology to detect movement of disks mechanically coupledto a spindle.

[0111] From FIG. 2, the current system comprises a base 201, having amounting block (not shown) or other holding device affixed thereto. Themounting block is fixedly mounted to a spindle 202. The rotating spindlemay maintain a plurality of media disks 204 (a) through (n), illustratedin further detail in FIG. 3, but may maintain a single disk or virtuallyany number of disks. In the configuration shown, ten disks are employedand are secured by locking cap 302 and chuck clamp 303. Positioner 401of FIG. 4 maintains a series of heads 403(a) through (n), typicallyindividual read/write heads that perform both reading and writingfunctions, where each head flies over the surface of the media 204(a)through (n), which are typically hard disks. A depiction of the entiresystem is presented in FIG. 5, wherein the positioner 401 is closelyassociated with the disk stack and a VCM motor 502 to read from andwrite to the disks.

[0112] In the current aspect of the present invention, an ideal disk(not shown) comprising positional guiding information, such as aparticular data and/or servo data track structure, is produced possiblyseparate and apart from the configuration illustrated in FIG. 3. Theideal disk may be produced using the FIGS. 2 through 5 configuration,but it is typically not produced in the same multi-disk situation asillustrated in FIG. 3.

[0113] According to an aspect of the invention, the ideal disk isproduced using patterning technology. In one case, the ideal disk isproduced using lithography methods, as employed in the semiconductorindustry. In another case, the ideal disk is produced using an electronbeam (e.g., the tracks on the disk are written using an electron beam).This ideal disk is used as a reference for the subsequent media readingand writing functions performed by the system of FIG. 1. If the idealdisk is a magnetic disk, the system reads magnetic reference data. Ifthe ideal disk is produced using patterning technology, lithography, oran e-beam, reading reference data from the disk may include employing adevice such as a laser positioning system employing, for example,reflection, refraction, or transmission, such as in the case wherephysical holes are placed in the ideal disk.

[0114] In one embodiment, the ideal disk produced using methodsdisclosed herein is then mechanically coupled to the spindle along withany other disks that may normally be coupled to the spindle. In aparticular application, a plurality of disks to be written or tested isarranged in a stacked formation and is mechanically coupled to thespindle. In this particular application, the ideal disk is alsomechanically coupled to the spindle to detect movement of the spindle,and implicitly, of one or more of the stacked disks. More than one idealdisk may be attached to the spindle to further improve the accuracy ofthe movement detection process. In the present arrangement, the systemhas predetermined knowledge of the parameters of the ideal, orreference, disk and uses the ideal disk to form a reference point fortracking the actual position of the spindle and media located thereon.Use of additional ideal disks provides further reference points to trackand eliminate media position irregularities.

[0115] A non-contact radiation detection system interacts with the idealdisk to detect movement of the ideal disk, and implicitly, of thespindle mechanically coupled to the ideal disk.

[0116] In one aspect of this non-contact radiation detection system, thenon-contact radiation detection system comprises an optical system,conceptually illustrated in FIG. 6. The optical system 601 comprises anoptical transmitter 602, such as a laser diode, and an optical receiver603, such as an optical detector. The optical transmitter and receivermay be disposed on the base of the system, such as at base 201, and maycooperate to detect movement of the ideal disk with respect to the base201. Depending on the structure and properties of the ideal disk, theoptical transmitter and receiver may be disposed on opposite sides ofthe ideal disk. For example, the positional guiding information may bederived from apertures that permit transmission of optical radiation.Alternately, positional guiding information may be derived from a sameside of the ideal disk. For example, the positional guiding informationand/or the ideal disk may exhibit reflective properties, and data may betransmitted to the disk surface and be reflected and interpretedtherefrom.

[0117] The optical system 601 detects movement of the ideal disk withrespect to the optical transmitter 602 and receiver 603. Hardware and/orsoftware logic utilizes the information provided by the optical systemto determine the magnitude and direction of movement at any point alongthe spindle or on the disks, both with respect to the base and withrespect to any heads operating on the disks. In one aspect, the opticalsystem may be affixed or mechanically interconnected to the base 201,and the optical system 601 knows the position of the base 201, thespindle, and the disks. The optical system monitors disk positionrelative to its own position and transmits any variations to hardwareand/or software logic to correct for perceived deviations based on thepattern observed from the ideal disk. Once the direction and magnitudeof motion of a particular disk is determined at a point proximate to acorresponding head reading from, or writing to the disk, the head movesaccordingly to compensate for disk motion. As a result, the systemminimizes or eliminates relative motion of the head with respect to themedia disk.

[0118] In a particular implementation, a voice coil motor (VCM) thatnormally engages and operates the head utilizes information provided bythe optical system 601 and/or other logic to move the head in responseto disk movement. In this implementation, the head is substantiallyrigidly coupled to an arm that moves under control of the VCM. Apositional difference in the ideal disk perceived by the optical system201 is provided to the VCM logic such that the head and arm are moved tocompensate for the perceived positional shift. In many situations, thepositional shift will be a rotation that is too fast or too slow,meaning the head is either ahead of or behind its desired position. Insuch a lead or lag situation, the rotation of the system may be alteredor the head shifted forward or backward in the rotation.

[0119] In an alternative implementation, the head is mechanicallycoupled via a jointed connection to a first end of the arm controlled bythe VCM, and the head may move (rotate or translate) with respect to thefirst end of the arm under the control of one or more actuators.

[0120] 2. Ideal Magnetic Disk Serving as a Reference for a Head

[0121] Another aspect of the present invention utilizes an idealmagnetic disk to detect movement of disks mechanically coupled to aspindle.

[0122] An ideal magnetic disk comprising positional guiding information,such as a preferred data and/or servo-data track structure, is producedaccording to an aspect of the present invention. The ideal magnetic diskmay be produced separate and apart from the multiple disk configurationof FIGS. 2 through 5, but this is not specifically required. The idealmagnetic disk having magnetic positional information located thereon isthen mechanically coupled to the spindle, in addition to any other disksthat may normally be coupled to the spindle. In a particularapplication, a plurality of disks to be written or tested is arranged ina stacked formation and is mechanically coupled to the spindle, as inFIG. 2. In this particular application, the ideal magnetic disk is alsomechanically coupled to the spindle to detect movement of the spindle,and implicitly, of one or more of the stacked disks. More than one idealmagnetic disk may be attached to the spindle to again improve theaccuracy of the movement detection process.

[0123] Thus the system may reduce relative movement between the head andthe ideal disk by either moving the spindle in combination with thedisk(s), or moving the heads. If moving the spindle, such movement maybe accomplished using an air pulse, a mechanical centrifugal device suchas a screw or actuator, varying the magnetic field in the spindleelectromotor, or varying the external magnetic field surrounding thespindle. If the system reduces relative movement by moving the heads, itemploys either jointed head arms having individual actuators locatedthereon, moving only the tip of the head arm, or alternately may movethe entire head arm.

[0124] According to one aspect of the invention, the ideal magnetic disk(not shown) is produced by writing a data or servo track in multiplerevolutions instead of writing the track in a single revolution.Commonly, a data or servo track may be written in a single revolution,but the track may exhibit random deviations from the desirable circularpattern. The random deviations may include non repeatable run out errorsthat may occur due to temporary and non-recurring factors. An aspect ofthe current invention is to provide for writing such a track duringmultiple revolutions by partitioning the track into multiple segmentsand writing different segments in different revolutions to average outthe random deviations. By writing different segments of the track duringdifferent passes, random errors introduced into the system by sourcesthat move the disks with respect to the heads are averaged out, therebybeing reduced or eliminated.

[0125] One aspect of the current invention associated with employing anideal magnetic disk as a reference is that of writing servo bursts inmultiple revolutions to average the adverse affects associated withservowriting, such as the problem of non-repetitive run out. This aspectrequires writing servo data in multiple revolutions. Under previouslyknown servowriting operation, when the system servowrites a track, theNRRO (non-repetitive run out) occurring during the servowritingrevolution is written into the track. The NRRO contribution can beminimized by averaging such writing over all or part of servowrittendata. Data writing averaging may be achieved by writing a servo burst inmultiple revolutions, with different portions of the servo data writtenin different revolutions.

[0126] In a particular implementation of the invention, one or moreportions of the servo data may be written multiple times insubstantially the same physical location on the disk during differenttracks. Writing a particular portion of servo data more than one timemay be desirable under various circumstances, including, for example, toassess characteristics of the disk and/or heads, or to improve theaccuracy of the track by further averaging out random errors. In aparticular embodiment, writing a particular portion of servo data morethan one time may be achieved by partially or fully overlapping datawritten to contiguous portions of the disk.

[0127] In operation, in one embodiment of the invention, the servowriterwrites a long track, such as a four-revolution track, during fourseparate revolutions. The segments written every revolution produce thefinal servo pattern. In one case, the system performs dynamic control ofthe write gate to avoid overwriting portions written in previousrevolutions, i.e. the write gate does not write when commanded under allconditions as had been done on previous systems. In another case, thesystem performs dynamic control of the write gate but permits partial ortotal overwriting of one or more portions written in previousrevolutions. The switching of head current in connection withembodiments disclosed herein may be performed at a significant rate,typically higher than that previously done. The rate at which the headcurrent is switched may be decreased in situations where the systemwrites data patterns comprising segments spaced further apart on thedisk.

[0128] According to this aspect of the invention, the system writesservo data multiple times over the surface of the disk. For example,servo data for a certain position of the disk may be written more thanonce, such as four times, to the same area. Alternatively, a particularsegment of data may be partitioned into multiple overlapping, contiguousand/or non-contiguous subsegments, and the subsegments may be writtenduring one or more different revolutions. In either case, should one ofthe writing functions suffer from non-repetitive runout, that writingfunction may be averaged with the other writing functions and the systemmay selectively read from the areas exceeding or not exceeding anaveraged threshold, or a combined threshold. This averaging techniquemay be achieved by writing the servo data multiple times over a singledisk.

[0129] FIGS. 7-10 illustrate further aspects of the system relating tothe concept of the averaging technique of an aspect of the invention.FIG. 7 shows normal operation of writing bursts to a track. Track 701 isthe target for writing and also subsequently for reading of informationusing a series of bursts. First burst 702, or Burst A, is written first,and second burst 703, or Burst B, is written thereafter. FIG. 7 is anideal version of the burst writing arrangement. In reality, tracks maybe neither perfectly straight nor perfectly circular, and burst writingis frequently inexact, off center, too short or too long, and/orotherwise imperfect. A more typical illustration is provided in FIG. 8,wherein burst A spans the track and Burst B is located entirely off thetrack. This effect makes reading and writing over the locations asimprecise and undesirable. A conventional write head writes a burst in asingle revolution, shown in FIG. 9 as Burst A 901. In reality, thisconceptual depiction of Burst A 901 may be inaccurate, as the head mayimpart a magnetic signal in the form of a typical sine wave to the trackand disk, such as that shown as magnetic signal 902.

[0130] Thus, according to the embodiments of FIGS. 7 and 8, writing ofBurst A and Burst B comprises writing a first set of data in a sine waveas Burst A and a second set of data in a sine wave on the opposite sideof the track as Burst B. The result may be sine waves disposed in variedorientation on the disk with respect to the track. In one case, once thehead writes Bursts A and B to the disk, the system positions the readand/or write head on the track and reads the A and B Bursts. S_(A) andS_(B) represent the energy perceived by reading Bursts A and B,respectively. In a particular implementation, the head passes thereceived energy for the two bursts to hardware and/or software tocompute the following energy value:

E=(S _(A) −S _(B))/(S _(A) +S _(B))

[0131] If the Burst A and Burst B energy levels are equal, this valuegoes to zero, indicating that Bursts A and B are located close to theirdesirable positions along the intended track. If the magnitude of energyE exceeds a particular threshold, the system may decide that theposition, shape, or other relevant characteristics of the track areunsatisfactory, and may choose to reposition the head and rewrite BurstsA and B. Correction of such position, shape, or other relevantcharacteristics of the track may be achieved and verified by decreasingthe magnitude of energy E.

[0132] Since the value of E may be positive or negative, in oneembodiment the system may utilize two different thresholds, depending onwhether E is positive or negative. The two thresholds may also be equalin magnitude but opposite in sign. The thresholds may be predeterminedbased on characteristics of the disk and/or system, or may bedynamically computed and/or adjusted along the tracks based oninformation that the system obtains while writing and reading tracks.The sign of E may be used to assess which of Bursts A or B is deviatingmore from a desirable position, and this assessment may be utilized toselect an appropriate corrective action. In one case, the system mayselect to only rewrite a particular burst. In other cases, the systemmay select to rewrite more than one burst, or a combination of completeand/or partial bursts. In other embodiments of the invention, othermethods may be employed to determine undesirable deviations in position,shape, or other relevant characteristics of the track, including morecomplex mathematical models and formulas for the energy E.

[0133] In previous systems, an inaccurately-written track would eithergo uncorrected or would require reading the written area, erasing badtracks, and again writing the data, but this could again have the datawriting errors such as those pictured in FIG. 8 and/or may waste timeand system resources.

[0134] According to one aspect of the present invention, the systemwrites the A and B bursts in multiple revolutions over the same diskarea. FIG. 10 illustrates writing a first sinusoidal dipulse 1001 forBurst A at the beginning of the desired Burst A location, followed by asecond dipulse 1002 for Burst B at the beginning of the desired Burst Blocation. On a second pass, the head writes the second Burst A dipulse1003 offset in position from the first Burst A dipulse 1001, possibly ator near the end of the first dipulse 1001 point. Second Burst B dipulse1004 is similarly written at a position offset from first Burst Bdipulse, and possibly at or near the completion point of the first BurstB dipulse 1002. The system can step through the Burst dipulses and maywrite more than one dipulse per pass, illustrated by the ellipsis inFIG. 10. Two passes may be employed, or more than two passes, within thescope of the present invention. Alternatively, the system may writepartial dipulses in various passes, or a combination of partial and fulldipulses.

[0135] The result of this partial burst writing technique employed onmultiple passes is to provide an averaged positioning and signalstrength for burst writing such that writing on a single pass with asingle offset becomes unlikely. Should one pass suffer from an offsetduring the writing procedure, that offset may be corrected or decreasedin subsequent passes.

[0136] A drive having a substantially-constant offset at all times, or abias, may be unacceptable and improperly operating. The system may electto correct this bias. Alternatively, such a bias may be detected andcommunicated to a disk drive comprising the respective disk, such thatthe disk drive may utilize the bias to follow the track comprising thebias. In one case, such a bias may be attributed to repeatable run offerrors.

[0137] The effect addressed by the present aspect of the system israndom noise or intermittent wandering experienced during writing undernormal operation. Over a number of passes, it is to be understood thatthe present aspect of the system tends to reduce adverse effects due toerrant dipulse and burst writing.

[0138] It is to be understood also that part of a dipulse may be writtenin one pass, or multiple dipulses, but in most cases the entire burstarea and all dipulses are not written in a single pass for a particulardata burst. Thus it is within the scope of the present system to write asubset of the pulse or a number of dipulses which is less than all ofthe dipulses to the disk in a first pass, then an additional dipulse ornumber of dipulses or portion of the burst or portions of the burst on asubsequent pass or multiple subsequent passes.

[0139] Once this multiple pass data burst writing technique iscompleted, the system may optionally compute the energy calculationprovided above for Bursts A and B. While the energy errors may be lessfor the disk written according to the multiple pass technique, shouldthe value of the energy computation be outside a particular range thebursts may need to be rewritten. This reading, energy computation,assessment, and rewriting is optional but may have a tendency to provideenhanced and improved burst writing capability.

[0140] With respect to the magnetic disk aspect of the present system,according to an aspect of the invention, once an ideal magnetic disk isproduced, the ideal magnetic disk is mechanically coupled to thespindle, possibly in addition to other disks to be written or testedstacked thereon, such as in the configuration illustrated in FIG. 1. Theideal magnetic disk spins together with the other disks. Alternatively,the ideal magnetic disk may not spin together with the other disks, butmay be offset by a predetermined, predictable or determinable amountwith respect to the other disks. As previously mentioned, more than oneideal magnetic disk may be utilized.

[0141] In one embodiment, a detector head reads information stored onthe ideal magnetic disk and detects movement of the ideal magnetic diskwith respect to the head. Hardware and/or software logic utilizes theinformation provided by the detector head to determine the magnitude anddirection of movement at any point along the spindle or on the disks,with respect to any heads operating on the disks. If the disk is aheador behind the point where it should be, for example, the differentialbetween the present position and the desired position is applied tohardware and/or software logic to either alter the spin of the disk oralter the head position to move into closer synchronization with thepreferred position. In other words, once the system determines thedirection and magnitude of motion of a particular disk at a pointproximate to a corresponding head reading from or writing to the disk,the system moves that head to compensate for the motion of the disk. Asa result, the relative motion of the head with respect to thecorresponding disk is reduced or eliminated.

[0142] In one implementation, a voice coil motor (VCM) that normallyengages and operates the head utilizes information provided by thedetector head and/or other logic to move the head in response tomovement of the disk. In this aspect, the head is substantially-rigidlycoupled to an arm that moves under control of the VCM. In an alternativeimplementation, the head is mechanically coupled to a first end of thearm controlled by the VCM via a jointed connection, and the head maymove with respect to the first end of the arm under the control of oneor more actuators.

[0143] The method for averaging out random errors by writing differentsegments of a track in multiple revolutions disclosed herein may beutilized in connection with one or more heads writing information to adisk. When multiple heads are utilized to write to a single disk, theheads may be distributed along a single arm controlled by a single VCM.Each head may be individually controlled by one or more correspondingactuators mechanically coupled to the arm. Alternatively, there may bemore than one arm, and each arm may be controlled by the same ordifferent VCMs.

[0144] While the description above has provided an example of how anaspect of the present invention may be employed to produce an idealmagnetic disk, the methods and systems disclosed herein may also beapplied to produce regular data disks. More specifically, the systemsand methods taught herein may be utilized by a commercial system towrite data to a disk prior to distribution of the disk to an end user,or by a disk drive comprised in a system utilized by an end user. Thesystems and methods disclosed herein and discussed in connection withFIGS. 7-10 may be employed to improve the accuracy with which datatracks are written in a variety of applications, aside fromcertification, initialization and servo writing of disks. For example,but without limitation, a desktop or a laptop computer system maycomprise a disk drive that utilizes methods and systems taught herein toimprove the reading and/or writing of regular data from and/or to adisk, such as operating system information, software and word processingfiles. As another example, a portable consumer device may employ methodsand systems taught herein to improve storage and/or retrieval of data toand/or from a disk, including audio, video, and/or communication data.

[0145] Certain modifications to the methods and systems disclosed hereinmay be made while remaining within the scope of the present aspects ofthe invention to more appropriately address particular characteristicsof the intended application. For example, in a mobile consumer devicethat may be commonly and repeatedly exposed to physical shocks due tophysical impacts or movements, the expression of the energy E and/or thecorresponding thresholds may be altered to tolerate a wider range ofdeviations in the position, shape, or other relevant characteristics ofthe data tracks, possibly at the expense of track density.

[0146] 3. Non-Contact Radiation Detection System that Bounces Radiationoff a Part of the Spindle

[0147] Yet another aspect of the invention provides a system and methodfor detecting movement of a spindle and/or one or more disks withrespect to a common base by detecting radiation reflected by a part ofthe spindle. Movement of the spindle and/or one or more disks withrespect to the common base may then be related to movement with respectto one or more read/write heads.

[0148] As described above, movement of the spindle with respect to thebase may result in relative movement between a disk and a correspondinghead writing to, or reading from the media disk, thereby possiblyinterfering with the operation of the head. In one embodiment, thesystem detects the magnitude and direction of such movement between adisk and a corresponding head and compensates for such movement bymoving the head accordingly.

[0149] One implementation of this aspect of the invention utilizes asource that directs radiation towards an area of the spindle and areceiver that detects radiation reflected by the area of the spindle.Hardware and/or software logic functionally connected to the transmitterand/or receiver detects movement of the spindle with respect to the baseand moves one or more heads reading from, or writing to the disksaccordingly.

[0150] In one aspect, the non-contact radiation detection systemcomprises an optical system. The optical system comprises an opticaltransmitter, such as a laser diode, and an optical receiver, such as anoptical detector. The optical transmitter and receiver are disposed orotherwise fixedly mounted to the base of the equipment and cooperate todetect movement (other than normal spinning) of the spindle with respectto the base.

[0151] A cylindrical area of the spindle exhibits a certain degree ofreflectivity. In one case, the cylindrical area is manufactured from areflective metal, such as steel, and is polished to exhibit a relativelyhigh degree of reflectivity. Alternatively, the cylindrical area of thespindle may be covered with a reflective material. The cylindrical areaof the spindle is substantially perpendicular to the planar surfaces ofthe disks stacked on the spindle. The spinning axis of the disks stackedon the spindle is substantially parallel with the cylindrical area andapproximately coincides with the central axis of the cylindrical area.Both the cylindrical area and the stacked disks are substantiallyrigidly connected to the spindle, such that the cylindrical area and thestacked disks spin with approximately the same angular speed.

[0152] The optical system detects movement of the spindle with respectto the base by illuminating the reflective cylindrical area with a laserbeam produced by the optical transmitter and receiving a reflectedportion of the laser beam at the optical detector.

[0153] Cross sections of the cylindrical area may not be perfectlycircular, but may exhibit irregularities, such as an oval,non-circularly-curved, or “egg” shape. To compensate for anyimperfections in the surface of the cylindrical area, the system in oneaspect analyzes the Fourier frequency spectrum of the light reflectedoff the cylindrical area and filters out periodic signals that may beattributed to imperfections of the cylindrical surface intercepting theincident laser beam periodically as the spindle spins at arelatively-high rate.

[0154] Another aspect of this reflective spindle configuration utilizestwo or more laser beams offset with respect to each other. Each laserbeam corresponds to a dedicated laser source and a dedicated laserdetector. Since imperfections of the cylindrical surface will exhibitsimilar signatures on each laser beam, as detected by the variouscorresponding laser detectors, these imperfections may be filtered outand the actual movement of the spindle with respect to the base may beisolated and detected or estimated.

[0155] One alternate aspect of the invention in addition to thoseoutlined above is using a series of ridges or non-reflective materialequally spaced around the cylinder such that light energy transmitted tothe cylinder reflects efficiently off reflective areas but does notreflect efficiently off the ridged or nonreflective areas. This enablesthe system to measure relative position and timing and correct errors bycounting the number and time of reflections provided.

[0156] Hardware and/or software logic may utilize variations in theintensity, frequency and/or phase of each reflected laser beam receivedat the corresponding detector to determine the magnitude and directionof movement at any point along the spindle or on the disks, both withrespect to the base and with respect to any heads operating on thedisks. The system can determine such parameters using an interferometerto detect movement of the spindle.

[0157] Once the direction and magnitude of motion of a particular diskis determined at a point proximate to a corresponding head reading from,or writing to the disk, the system moves the head to compensate for themotion of the disk. As a result, the relative motion of the head withrespect to the disk is minimized or eliminated. In a particularimplementation, a voice coil motor (VCM) that normally engages andoperates the head utilizes information provided by the optical systemand/or other logic to move the head in response to movement of the disk.In this aspect, the head may be substantially-rigidly coupled to an armthat moves under control of the VCM. In an alternative implementation,the head is mechanically coupled to a first end of the arm controlled bythe VCM via a jointed connection, and the head may move with respect tothe first end of the arm under the control of one or more actuators.

[0158] According to an embodiment of the invention, multiple heads areutilized to write to a single disk, and the heads may be distributedalong a single arm controlled by a single VCM. Each head may beindividually controlled by one or more corresponding actuatorsmechanically coupled to the arm. Alternatively, there may be more thanone arm, and each arm may be controlled by the same or different VCMs.In each of these implementations, the system may utilize the informationobtained regarding the magnitude and direction of relative movementbetween a particular head and a corresponding disk to reposition thehead and/or disk dynamically.

[0159] An alternative aspect of spindle position measurement providesalternate differential systems to detect spindle movement with respectto the base. The differential system for detecting motion of the spindlemay, for example, comprise two or more laser beams reflecting offdifferent portions of a reflective or alternatingreflectivity/nonreflectivity part of the spindle to detect the magnitudeand direction of spindle movement at different points in the system.

[0160] As a further feature of the present design, the system performsvarious functions designed to minimize repeatable run out and/or nonrepeatable runout errors (RRO and NRRO). RRO and NRRO are measurementsof the radial accuracy of written tracks. RRO and NRRO measurements maybe performed after the system has written to the disk, and can beassessed by assembling the written disks into drives and testing.Components such as the spindle may also be tested independently toinsure runout error is within predetermined specifications, but thisagain typically occurs after the write operation. Such measurements aregenerally not made during the servowriting process. In some cases, a fewbasic runout performance values can be made available after writing theservo pattern by reading the radial positioning error with the samemagnetic read/write head on the servowriter used to write data. Thesystem then records the standard deviation of the RRO and NRRO for thejust-written tracks.

[0161] The present system monitors runout performance duringservowriting. The runout error signal may be used for a follow upcorrection indication so that improperly written data, such as a servomark, can be rewritten. Rewriting miswritten data tends to limit thetail of the runout error statistical distribution, thereby enablingtighter overall error distribution and therefore smaller track spacing.

[0162] For simultaneous monitoring of radial track positioning errors,the system generally cannot use the read/write head during the writingprocess. Various supplemental optical or capacitive sensors monitor thespindle axis position with respect to a base, reference spindle axisposition, or a surface that emulates the head position with respect tospindle axis position. This relative measurement may be performed using,for example, a single beam or differential beam interferometer asdiscussed herein. Other routine position monitoring devices such ascapacitance probes, inductive sensors or alternate optical positionsensors could also be employed to monitor spindle position.

[0163] Performance metrics for track writing performance may beexpressed in terms of the standard deviation of radius from a demandedradius. This standard deviation can be separated into repeatable andnonrepeatable components for purposes of measuring/correcting. Inaddition, numerous monitoring and performance metrics have not beenpreviously implemented on data writing devices such as servowriters.

[0164] An aspect of the invention provides a method and system fordetermination of a monitoring and performance metric for assessing trackdata: the time or RPM dependent servo mark positions, or opticallyinferred spindle axis position. Since disks are mechanically coupled tothe spindle, the position of the axis of the spindle may be reliablycorrelated with the position of a servo mark located on any particulardisk, and such a correlation is bi-directional in the sense that knowingeither of the two enables determination of the other one.

[0165] According to various aspects of the present invention, assessingtime or RPM dependent servo mark positions or optically inferred spindleaxis positions can be accomplished in different ways. In a particularimplementation, an optical sensor can be used to monitor the position rof the spindle chuck or hub surface and record r(θ(t)) as the spindlechuck spins with angular velocity ω. The topographical radiusr_(t)(θ)=r_(t)(ωt) of the surface as a function of angle θ can bedetermined independently. The difference:

δr(t)=r(θ(t))−r _(t)(θ)

[0166] expresses the amount of wobble in the disk axis.

[0167] This wobble can be divided into two components: a repeatable parthaving harmonics of the basic rotational rate given by the followingFourier components

A _(N)(ω)=(2π)⁻¹Σ_(i) exp(iNωt _(i))δr(t _(i));

δr _(rro)(t _(i))−ΣiN exp(−iNωt _(i))A _(N)(ω).

[0168] and a non repeatable part including nonharmonic components

δr _(rro)(t _(i))=δr(t _(i))−Σ_(N) exp(−iNωt _(i))A _(N)(ω)

[0169] With respect to the repeatable portion, A_(N)(ω) is the amplitudeof the spindle wobble at a frequency of Nω. This value may not beconstant but may change slowly with time. The media writer or servowriter has the ability to monitor this amplitude during writing forprocess control, grading, media writer self testing, or for activelycontrolling the media writer as disclosed herein using this repeatableportion amplitude. For example, active control of the media writer mayoccur by putting a deflection on the voice coil to place a compensatingposition on the writer head.

[0170] Another example of employing processed data in servowritingperformance is using the histogram of the NRRO component (non-repeatablepart of the wobble that includes the nonharmonic components) of theservo mark positions or optically inferred spindle axis position. Inthis arrangement, an optical sensor such as an interferometer monitorsthese non repeatable errors during servowriting. The width and shape ofthis distribution assesses data writer performance as well as thequality of the servo patterns on the disk.

[0171] 4. Radial Positioning Using Interferometer

[0172] Yet another aspect of the invention provides a system and methodfor detecting movement of a spindle and/or one or more disks withrespect to one or more read/write heads by detecting radiation reflectedby both a part of the spindle and one or more features mechanicallycoupled to one or more of the heads. One embodiment of the inventionemploys an interferometer in performing radial positioning functions.The present design enables in-situ monitoring of the disks and allowscertification by offering dynamic compensation for spindle movement.

[0173] In an alternative implementation, information regarding movementof the spindle and/or heads with respect to a common base obtained aspreviously described may be employed together with data obtainedaccording to the embodiment further described in this section to furtherimprove the accuracy and/or reliability of the measurements.

[0174] In common implementations, interferometers are devices thatconvert the phase difference between two input waves into intensityvariations on one or more output waves that carry information about thephase difference between the input waves. The interferometer outputs mayrepresent superpositions of portions of the two input waves. The amountof each input delivered to each output and the phase shift impartedduring delivery correlates to the optical path length difference betweenthe two beams.

[0175] One type of interferometer that may be used in the present systemis that described in U.S. patent application Ser. No. ______, entitled“Waveguide Based Parallel Multi-Phaseshift Interferometry for High SpeedMetrology, Optical Inspection, and Non Contact Sensing,” inventors DavidPeale, et al., assigned to the assignee of the present invention, whichis hereby incorporated by reference into the present application. Theinterferometer of this aforementioned application is a multiphaseinterferometer that employs waveguided optics and an optical coupler toproduce a tri-phase signal that enables measurement of phase differencesbetween two emitted beams.

[0176] One aspect of the invention disclosed herein is to measure thedistance of the head to the disk axis, or spindle, as accurately anddirectly as possible. Direct measurement comprises using as actual adistance measure of the head position as possible, with as littleindirect or calculated measurement as may be performed under thecircumstances. One aspect of the present invention is illustrated inFIG. 11. From FIG. 11, the system employs an optical interferometertransmitting two laser beams in a differential mode. Interferometer 1101comprises a laser light generating source, and possibly more than onesuch source, to generate two separate laser beams. The first laser beamstrikes a first lens 1102 and a second focusing lens 1103 and directsthe resultant beam to the polished chuck 1106. Polished chuck 1106typically comprises a highly reflective or mirror like surface. Thesecond beam passes through third lens 1104 and is retro reflected from acorner cube 1105 or other retro reflecting surface mounted on thee-block, illustrated in FIG. 4 as element 404. A corner cube, or cat'seye, operates under the law of reflection, but operates differently froma typical mirror or reflective surface. A beam of light entering thecorner cube is reflected back in the same general direction as its angleof entry. This same-direction reflection occurs for not only one specialangle of incidence with a mirror, but for all angles of incidence withthe corner cube. The second beam in FIG. 11 is typically collimated, oremits energy waves that are substantially parallel. Mounting the retroelement, such as corner cube 1105, to the e-block, is performed in anorientation that emulates the head position. In other words, the retroreflective element is mounted in a position on the positioner or e-blockthat emulates the position of the read/write head, and the stiffness ofthe positioner arm and connection between the e-block position and theread/write head offers a substantial analogy to actual head position.The retro reflector or corner cube 1105 swings in an arc tangent to thesecond, substantially collimated, interferometer beam, and reflects backthrough third lens 1104 and back to the interferometer, where the timeof reflection or distance from the interferometer 1101 to the emulatedhead position is determined. The resultant interferometer signalsubstantially measures the distance between the surface of the chuck orchuck spindle 1103 and the simulated head position at the retroreflector or corner cube 1105. The difference between the interferometerand the chuck minus the distance between the emulated head and theinterferometer is δraw, or the raw measurement of head position relativeto the polished chuck 1106.

[0177] The difference signal δraw must be corrected for topologicalparameters of the polished chuck 1106. The chuck 1106 can deviate from aperfect and exactly centered cylinder, and under certain circumstancesmay move or shift during operation. The system measures deviationindependently as a function of disk angle, Θ, and the measurement isdynamically stored in memory. Deviation of the cylindrical chuck isrepresented by δtopo(Θ). The system then computes the error signal basedon the difference between the raw position of the emulated head minusthe topographical error of the disk cylinder, δerr=δraw−δtopo(Θ). Thiserror signal is employed by the system to actuate the voice coil 1107and micro actuators on the suspension to reposition the head to moreaccurately track the radius of the true axis of the disk. The errormeasurement is factored into the desired position of the head to affectmovement of the head to a more exact position over the disk. Inaddition, that portion of the error signal at frequencies too high forthe positioning servo to correct for can be used to inhibit writing ofthe servo information if this signal is above a predetermined limit.Writing of the servo information may recommence once the error signalfalls below the limit.

[0178] In an alternate aspect of the present design, an additionalinterferometer is employed above the disk to provide a z-axismeasurement and to address issues of tilt. In this embodiment, the retroreflector or corner cube is located at a different height than thelateral version to measure differential z position caused by tilt. Thesecond interferometer also uses lensing to set up a collimated beam andtracks a reference Z point, which may be disk position or spindlelocation, or some other available reference height point on thearrangement. The measurement at an additional axial position (z) is fedback to the signal processor and the voice coil is employed to correctthe head position over the disk. If the system measures the tilt of arotating spindle, signal processing requires the raw positional zmeasurement minus the topographical shift resulting from tilt. Dependingon the parameter desired to be measured, whether head position, spindleposition, or disk position, the retro reflector must be positioned tooffer an accurate representation of the target parameter. Thus if zposition of the head is the desired parameter to be measured, the retroreflector positioning must, like the aspect described above, emulate thehead position, such as on the e-block or otherwise associated asdirectly as possible with the positioner and/or read/write head.Alternately, if tilt of the spindle is the desired measured parameter,one beam may reflect off approximately the top center point of thespindle, for example, while the second beam reflects off a point as farto the periphery of the spindle as possible.

[0179] In another alternate aspect of the present system, a secondlateral interferometer is used with the system illustrated in FIG. 11,with a 90 degree difference between the first interferometer and thesecond to measure y axis movement in addition to x axis movement.

[0180] Unless indicated or implied otherwise, as used herein, x and ydirections are conventionally assumed to indicate directionssubstantially in the plane of a particular disk, while the z directionindicates a direction substantially parallel with the axis of thespindle. In particular embodiments, more than one substantially-parallelx-y planes may be considered when more than one disk is coupled to thespindle. Depending on the context, the angle theta (θ) may beconventionally defined in a particular x-y plane, or may be aspindle-characteristic value that is common to all disks coupled to thespindle.

[0181] This aspect of the invention uses an additional retro reflectoror corner cube mounted on the e-block or other available and practicallocation to emulate head position and retro reflect the incomingcollimated beam. The interferometer again passes energy through alensing arrangement to focus and/or collimate the beams, and one beam isalso directed toward the spindle arrangement. This x-y dualinterferometer arrangement provides additional accuracy, and similarparameters are fed to the signal processor and used to command the voicecoil to more accurately position the e-block, positioner, and associatedread/write heads.

[0182] An embodiment of a system employed as taught herein to attainhigh accuracy positioning may include a dual beam interferometer asdescribed in the Peale application, U.S. patent Ser. No. ______. ThePeale design uses a tri-coupler where the reference beam of thetri-coupler is collimated onto a retro-reflector mounted to the E-Blockdescribed previously and the other beam is focused onto the spindle hub.

[0183] More specifically, the guided wave interferometer is a systemcomprises a tri-coupler and has the following aspects. The tri-couplerconsists of three waveguide inputs, three waveguide outputs, and aregion between the inputs and outputs wherein waves from each of thethree inputs are redistributed approximately equally to each of thethree outputs. Assuming that the tri-coupler is lossless and distributeslight from an input waveguide equally to each of the three outputwaveguides, then there may be a 120 degree phase shift between each ofthe three output light waves. Thus, if light is injected into two of theinput waveguides, the intensity of the light in the three outputwaveguides will possess a periodic interferometric modulation as thephase difference between the input beams advances, and in particular,the phase relation among the intensities of these three beams will be120 degrees. It is thus possible to measure the intensities of the threeoutput beams, and accurately determine the phase difference between thetwo input beams. In addition, the total intensity of the input light canalso be calculated.

[0184] Referring to the drawings more particularly by reference numbers,FIG. 14 is a schematic cross section through one section of afused-fiber optical tri-coupler 10 showing the spatial symmetry of thethree fibers 12, 14 and 16, leading to the characteristic 120 degreephase relation between the light waves within each of the threewaveguides. The tri-coupler 10 couples light between the first 12,second 14 and third 16 waveguides such that light input at one end ofany waveguide is substantially equally distributed to each of the threewaveguides at the output end.

[0185]FIG. 15 shows an embodiment of an optical interferometer 50 of thepresent invention. The interferometer 50 may include a first waveguide12, a second waveguide 14 and a third waveguide 16. The waveguides maybe fiber optic cables or integrated waveguides that transmit light.

[0186] One of the waveguides, namely the second waveguide 14, may becoupled to a light source 18. By way of example, the light source 18 maybe a laser. The light source 18 may have a return isolator 19 thatprevents back reflections from feeding back into the source 18. Thelight emitted from the light source 18 and isolator 19 may be directedinto the tri-coupler 10 via an optical circulator 22.

[0187] Light entering the tri-coupler 10 along waveguide 14 isdistributed to each of the three output waveguides in roughly equalintensities. Light exiting the tri-coupler on waveguide 14 is allowed toescape the waveguide unused, and the waveguide is terminated in such away that minimal light is reflected back into the tri-coupler. The lightexiting the first waveguide 12 is reflected from an object surface 24back into the waveguide 12. The interferometer 50 may include a lensassembly 26 and autofocus system 38 that focuses the light onto surface24 and back into waveguide 12. Light within the third waveguide 16 maybe reflected from a reference surface 27 back into the waveguide 16. Theobject 24 and reference 27 surfaces may be separate locations of thesame test surface. Alternatively, the light from the third waveguide 16may be reflected from a reference surface (not shown) separate from theobject surface 24.

[0188] The light reflected from the test surface 24 and referencesurface 27 through the first 12 and third 16 waveguides travels backthrough the tri-coupler 10. The reflected light within the firstwaveguide 12 provides an object beam. The light within the thirdwaveguide 16 provides a reference beam that interferes with the objectbeam within the tri-coupler 10.

[0189] The tri-coupler 10 allows reflected light within the firstwaveguide 12 to be coupled into the second 14 and third 16 waveguides,and reflected light from the third waveguide 16 to be coupled into thefirst 12 and second 14 waveguides. The output of the tri-coupler 10 isthree light beams with intensities that are out of phase with each otherby approximately 120 degrees. The light intensity of each light beamdetected by photodetectors 28, 30, and 32. The light exiting thetri-coupler along waveguide 14 is directed to the detector 28 via thecirculator 22.

[0190] Photodetectors 28, 30, and 32 provide electrical output signalsto the computer 34. The computer 34 may have one or more analog todigital converters, processor, memory etc. that can process the outputsignals.

[0191] By way of example, the interferometer 50 can be used to infer thedistance between the retro-reflector mounted on the E-Block and thesurface of the spindle hub where the surface of the spindle hub 24 is atthe focus and the retro-reflector 27 returns the collimated beam.

[0192] The differential distance (modulo λ/2) at any point can beinferred from the following equation.

h=λ*θ/4π  (1)

[0193] where:

[0194] h is the apparent differential distance;

[0195] θ is the interferometric phase angle between the object andreference beams, and

[0196] λ is the wavelength of the reflected light.

[0197] The interferometric phase angle can be determined by solving thefollowing three equations.

I1=α1(E1²+(β1E2)²+2β1E1E2cos(θ−Φ1)  (2)

I2=α2(E1²+(β2E2)²+2 β2E1E2cos(θ−Φ2))  (3)

I3=α3(E1²+(α3E2)²+2β3E1E2cos(θ−Φ3))  (4)

[0198] where:

[0199] I1=is the light intensity measured by the photodetector 28;

[0200] I2=is the light intensity measured by the photodetector 30;

[0201] I3=is the light intensity measured by the photodetector 32;

[0202] E1=is the optical field of the light reflected from the testsurface into the first waveguide 12;

[0203] E2=is the optical field of the light reflected from the testsurface into the third waveguide 16;

[0204] Φ1=is the phase shift of the detected light within the firstwaveguide, this may be approximately −120 degrees;

[0205] Φ2=is the phase shift of the detected light within the secondwaveguide, this may be defined to be 0 degrees;

[0206] Φ3=is the phase shift of the detected light within the thirdwaveguide, this may be approximately +120 degrees;

[0207] α1=is a channel scaling factor for the first waveguide anddetector;

[0208] α2=is a channel scaling factor for the second waveguide anddetector;

[0209] α3=is a channel scaling factor for the third waveguide anddetector;

[0210] β1=is a coupler nonideality correction term for channel 1;

[0211] β2=is a coupler nonideality correction term for channel 2, and

[0212] β3=is a coupler nonideality correction term for channel 3.

[0213] The interferometer 50 may include a phase shifter 36 that shiftsthe phase of the light within the third waveguide 16. The phase shifter36 may be an electro-optic device that can change the phase to obtain anumber of calibration data points. The calibration data can be used tosolve for the phase shift values Φ1, and Φ3, the channel scaling factorsα1, α2, and α3, and the coupler nonideality factors β1, β2, and β3. Thevalues are stored by the computer 34 and together with the measuredlight intensities I1, I2, and I3 are used to solve equations 1, 2, 3,and 4 to compute the phase angle, θ and the apparent distance h.

[0214]FIG. 16 shows an alternate embodiment of an optical interferometer60 of the present invention. The interferometer 60 uses a 2×2 opticalcoupler 23 in place of the circulator 22 used in interferometer 50. Inthis case, light from the laser is split as it passes forward throughcoupler 23. Light exiting coupler 23 along waveguide 15 is discarded.Light exiting coupler 23 in waveguide 13 is fed into tri-coupler 10 asin the interferometer 50 previously discussed. Light returning fromtri-coupler 10 along waveguide 13 is split. Light exiting coupler 23along waveguide 13 is rejected by isolator 19 and does not interferewith the laser. Light exiting coupler 23 along waveguide 15 is fed todetector 28. This embodiment of interferometer 60 may be less expensiveto produce than that of interferometer 50 owing to the fact that coupler23 may be considerably less expensive than circulator 22. However, thelaser power delivered into the tri-coupler 10 may be correspondinglyreduced and the signal detected by detector 28 may also be reduced ascompared to those detected in detectors 30 and 32.

[0215] The output signals of the photodetectors 28, 30, and 32,responding to a steadily advancing phase angle at the inputs, are shownsuperimposed in FIG. 17. The phase shifts between different light beamsseparates the maxima and minima of the output signals. With such anarrangement at least one of the signals will be in a relativelysensitive portion of the waveform between a maximum and minimum. Thisillustrates how the present invention provides an interferometricdetector that has a relatively uniform sensitivity and is thereforedesirable for metrological applications.

[0216] Interferometers 50 and 60 of the present invention provide threeout-of-phase signals with a minimal number of parts. The tri-coupler 10and fiber optic waveguides 12, 14, and 16 can be packaged into arelatively small unit, typically measuring only 0.12 inches diameter bytwo inches in length. This reduces the size, weight and cost of theinterferometers. By way of example, the tri-coupler 10 and waveguides12, 14, and 16 could be also constructed onto a single planar substrateusing known photolithographic and waveguide fabrication techniques. Sucha construction method would have advantageous properties which wouldallow tighter integration with other portions of the interferometricsystem together with reduced assembly costs.

[0217] As an alternative to those aspects discussed herein usinginterferometers, other sensing means or sensors may be employed todetect head position, using independently positioned detectors. Such aconstruct may employ fiber optics where the fibers are in closeproximity to the head and/or spindle. In such a design, the position ofthe spindle and heads are generally known to a degree. Light energy orother energy may be directed toward, for example, a head, and energyreflected off the head and received by a sensor located proximate ornear the head in the zone of expected energy reflection. Capacitancesensors or inductive sensors could also be employed in the design. Ingeneral, any three independent position detectors could be used todetect head position or spindle position in this design.

[0218] The present aspect of the invention is not limited to thespecific constructions and arrangements shown and described, sincevarious other modifications may occur to those ordinarily skilled in theart. For example, although the light reflected from the test surface 24is initially directed through the tri-coupler 10, it is to be understoodthat the light can be introduced to the test surface 24 withoutinitially traveling through the coupler 10.

[0219] Adjustment of Spindle Position

[0220] Various aspects of the invention described herein provide methodsand systems for directly on indirectly determining relative motionbetween one or more heads and one or more corresponding disks. In atypical case, one or more heads are operationally coupled to a diskreading to or writing from the disk, and a system provided by anembodiment of the present invention attempts to accurately position theone or more heads on the disk by identifying and minimizing oreliminating positional error interferences. In particular embodiments,the system operates substantially simultaneously on more than one disk.In the embodiments previously disclosed, correction of positional errorshas been generally achieved by repositioning the heads.

[0221] An aspect of the present invention provides an alternative methodfor correcting positional errors between heads and disks, namely, ratherthan repositioning a head, the system may reposition the spindle.Alternatively, the system may reposition both the head and the spindle.In a general case, according to an embodiment of the invention, thesystem may reposition each head in the system while,substantially-simultaneously, also repositioning the spindle. In thisgeneral case, there may be more than one head operationally coupled toeach disk, and each of these heads may be individually repositioned.

[0222] Cooperative repositioning of heads and spindle may help reduce oreliminate positioning errors with respect to each disk on which thesystem operates, and therefore may improve reading and writing of datato each such disk. In a servowriting and/or certification system, butalso in any other commercial or end user system or application, this mayimprove system performance, such as increasing the track density and thethroughput, and may reduce costs.

[0223] In one embodiment, as the system tracks positioning errors foreach disk and head in the system, the system may elect to solelyreposition the spindle without repositioning any of the heads in thesystem. This may occur when the system determines that repositioning ofthe spindle may satisfactorily reduce all or sufficiently many of thepositional errors associated with individual heads in the system withoutrepositioning any of the individual heads. This may be a more efficientand faster solution to correcting positioning errors during operation ofthe system as compared to individually adjusting the position ofindividual heads.

[0224] Movement of the spindle may be an effective approach to resolverepeatable run out errors. One cause for repeatable run out errors is animbalance in the mass distribution of the spindle and disks. An aspectof the invention may reduce positioning errors attributed to repeatablerunout by addressing and attempting to compensate for imbalances in thespindle and/or disk mass distribution.

[0225] Various embodiments of the invention provide methods and systemsfor repositioning a spindle to address positioning errors in the system.Once an error is detected, the spindle may be moved using conventionalmeans while rotating, including but not limited to using anelectromotive force (EMF) to alter spindle position. In oneimplementation, the spindle motor that normally drives the spindle torotate the disks coupled to the spindle may move the spindle in anyarbitrary direction. For example, the spindle motor may move the spindlealong the spindle axis, in the plane of any particular disk coupled tothe spindle, or in an arbitrary three dimensional spatial direction.Such an arbitrary three dimensional direction may include displacementboth in a plane that substantially comprises the spindle axis and in anx-y plane that substantially comprises the surface of a particular diskcoupled to the spindle.

[0226] In one embodiment, the spindle may be moved by altering thecurrent through the spindle motor coil. In one embodiment, the spindlemay be moved using one or more electromagnets disposed in proximity ofthe spindle to interact with the spindle and move the spindle via amagnetic field. In one implementation, at least three externalelectromagnets are disposed around the spindle, and the threeelectromagnets cooperate to produce magnetic fields of arbitraryorientations and intensities that may move the spindle in any threedimensional arbitrary direction. In one embodiment, permanent magnetsare mechanically coupled to the spindle to interact with the externalelectromagnets. In another embodiment, one or more spindleelectromagnets are mechanically coupled to the spindle to interact withthe external electromagnets. Electromagnets coupled to the spindle mayalso interact with external permanent magnets. Any combination andnumber of permanent magnets and electromagnets may be mechanicallycoupled to the spindle and/or disposed along the spindle. To repositionthe spindle, the system may vary electric currents through such spindleor external electromagnets to produce appropriate variations in themagnetic fields interacting with the spindle, thereby moving the spindleas desired.

[0227] Various devices may be utilized as electromagnets, includingHelmholtz Coils, magnetic coils with or without cores, and others.Generally, and device or combination of devices that produce a magneticfield with an adjustable intensity, gradient, and/or orientation may beutilized as described herein to move the spindle. Some of theembodiments disclosed herein insulate sensitive system components fromthe magnetic fields produced by permanent magnets and/or electromagnetsto avoid interference. The system components that may be protected frommagnetic fields include actuators, read and/or write heads, and othercomponents sensitive to electromagnetic interference.

[0228] According to an aspect of the invention, a spindle may also bemoved mechanically, via physical forces. In one aspect, variable airpressure through the orifices of the air bearing could be employed tocontrol and correct spindle positioning.

[0229] An embodiment of the invention utilizes actuators embedded in thespindle to redistribute the mass of the spindle and disks. In one case,if the system determines an imbalance in the mass distribution of thespindle that produces a repeatable run out error on one or more disks,the system may activate one or more actuators disposed along the spindlesubsystem to rebalance the mass distribution. This may be achieved byextending and/or retrieving one or more objects via actuators withrespect to the spindle axis. In a particular implementation, forexample, the system may extend an actuator beyond the circumference ofthe rotating spindle, thereby adding mass in a particular radialdirection of the spindle. Adding mass in particular radial direction ofa rotating spindle would increase the local centrifugal force, therebyproducing an additional local force, which could be utilized to move thespindle. The reverse effect could be achieved by retrieving an actuatorinside the circumference of a rotating spindle, thereby decreasing thelocal centrifugal force.

[0230] One embodiment may include altering spindle position byinteracting with the spindle via particles that exhibit mass. In aparticular implementation, the system may utilize air bursts or otherfluid bursts produced by one or more sources disposed in proximity ofthe spindle to move the spindle. Such an arrangement may employ a nozzleor nozzles, and may require submerging the spindle and/or media influid.

[0231] According to an aspect of the invention, any combination of themethods and systems disclosed above for moving a spindle may be utilizedto reposition the spindle alone, or in further combination withrepositioning of any group of one or more individual heads. For example,in one case, mechanical actuators may be employed to rebalance a spindlesystem exhibiting a mass-induced repeatable run out error, while acombination of magnetic devices actively reposition the spindle andindividual heads are repositioned with respect to particular disks.

[0232] Multiple Sector Servo Writing

[0233] Another aspect of the invention disclosed herein seeks to improvedisk manufacturing yield by writing multiple sets of servo sectors ordata sectors to the disk in a single revolution and then selecting theset of servo sectors exhibiting the highest data integrity. This aspectof the present invention applies to various types of data storageemploying circular media, including but not limited to magnetic disksystems, optical disk systems, and the like. The use of a singlerevolution to write data to circular media and subsequent selection ofspecific sectors of the media is applicable to any circular mediawriting system.

[0234] An aspect of the current invention provides a method forincreasing magnetic disk yield during the manufacturing process. Duringthe media disk formatting phase, the system writes a set of servosectors to the disk to provide a structure that guides writing and/orreading of data to the disk in subsequent phases. Generally, the numberof servo sectors on a particular disk is the same as the number of datasectors. According to one embodiment, each servo sector 1201 correspondsto a data sector and is comprised within the data sector 1202 as shownin FIG. 12. Conventionally, the servo sector 1201 is located at thebeginning of the data sector, as perceived in the angular direction ofrotation of the disk. Physically, both the data sector 1202 and theservo sector 1201 are shaped as partial substantially-circular sectors,but the servo sector 1201 subtends a significantly lower angle andoccupies a correspondingly lower overall area. The servo sectorscomprised in the set of servo sectors written to the disk during theformatting stage are disposed at substantially regular angular offsetpositions around the disk, a representation of which is illustrated inFIG. 13. More or fewer servo sectors may be written to the diskdepending on system requirements, but the important characteristic ofthis aspect of the invention is that servo data is disposed around thedisk during this single revolution initial formatting stage.

[0235] According to an aspect of the present invention, once the systemhas written the set of servo sectors to the disk, the servowriterverifies data written in the servo sectors to validate the disk. If thedata written within the servo sectors exhibits sufficient integrity, theservowriting process is considered successful, and data sectorscorresponding to the servo sectors are produced and validated. The datasectors may store data subsequently written to the disk.

[0236] According to an aspect of the present invention, more than oneset of servo sectors is written to the disk in the formatting phase,preferably during the same revolution. As a result, instead of a singleset of servo sectors disposed at substantially regular angular positionsaround the disk as shown in FIG. 13, the method disclosed hereinproduces one or more additional sets of servo sectors, each of theseservo sectors being also disposed at substantially regular angularpositions around the disk with respect to other servo sectors within thesame set. Alternatively stated, this method produces duplicates of theoriginal set of servo sectors, wherein each servo sector comprised in aduplicate set is offset by a constant angular amount with respect to acorresponding servo sector in the original set of servo sectors. Forexample, if the original set of servo sectors comprises a total of 36servo sectors, the beginning of each servo sector is offset from thebeginning of the preceding servo sector by ten degrees. A duplicate setof servo sectors would comprise a total of 36 duplicate servo sectors,and each of these duplicate servo sectors would be offset with respectto the preceding duplicate servo sector by ten degrees. If, for example,the duplicate set of servo sectors is disposed on the disk such that aparticular duplicate servo sector is offset from a particular originalservo sector by three degrees, each subsequent duplicate servo sectorwill also be offset from a corresponding original servo sector by threedegrees. In an alternative implementation, individual servo sectors maybe offset at arbitrary intervals, but the system may need to store moreinformation regarding the actual position of such servo sectors.

[0237] Upon writing one or more duplicate sets of servo sectors to thedisk, the system proceeds to verify the integrity of the data written toeach servo sector. One way of verifying the integrity of this data is toread the data and compare it against the data originally written to thedisk. The system then selects the set of servo sectors exhibiting thehighest degree of data integrity and erases or discards all other servosectors. Depending on the result of the verification process, the systemmay elect to retain the original set of servo sectors, or may retain oneof the duplicate sets of servo sectors. After erasure, the disk may beremoved from the servowriter and located in a hard disk drive, or if ina disk drive originally, the disk may remain therein and operatenormally. The system comprising the media disk may then utilize theselected set of servo sectors as a basis for further operations on thedisk, including data storage to the disk.

[0238] Another aspect of the invention utilizes the writing and readingconcepts disclosed above to increase the data storage capacity of a diskby writing multiple duplicate versions of data to the disk in differentdata sectors around the disk, and then retaining only the dataexhibiting a sufficient degree of integrity. This aspect of theinvention applies the method described above to regular data commonlystored on magnetic disks, such as computer operating system data or aword processing file stored on a hard disk, rather than just to servodata. In this aspect of the invention, similar to the servowritingaspect outlined above, more than one set of data sectors is written tothe media disk during normal operation, preferably during the samerevolution. As a result, instead of a single set of data sectorsdisposed at predetermined positions around the disk based on availablespace on the disk, this aspect of the method disclosed herein producesone or more additional sets of data sectors, each of these data sectorsbeing also disposed at predetermined and available positions around thedisk with respect to other data sectors. The system in this aspect ofthe invention writes data, here called “associated data,” to availableareas of the disk using an associated data header to indicate thebeginning of the data area. As used herein, the term “associated data”indicates data located on a media disk surface typically associated withother data on said media disk surface, as differentiated from the term“data,” which indicates data generally, associated or unassociated.Associated data subsets are located at available positions around thedisk with information correlating such associated data with similarlyassociated data. The system writes a second set of data with apredetermined header indicating the beginning of said data and writesthe remaining data around the disk to available locations. Data includedin this second group may be spaced at different locations around thedisk, but the data is associated with the second group and second headersuch that it can be retrieved appropriately. The result is two identicalsets of data written to the disk, with header information indicatingthat the associated data is identical but separate, along withinformation specifically associating the separate but identicalgroupings of associated data.

[0239] Alternatively stated, this method produces duplicates of theoriginal set of data sectors, wherein each data sector in a duplicateset is offset with respect to a corresponding data sector in theoriginal set of data sectors. The data sectors are not necessarilyequally offset from one another, but rather may be randomly offset andbroken apart in different configurations.

[0240] Upon writing one or more duplicate sets of data sectors to thedisk, in one embodiment, the system proceeds to verify the integrity ofthe data written to each data sector. One way of verifying the integrityof this data is to read the data and compare it against the dataoriginally written to the disk. The system then selects the set of datasectors exhibiting the highest degree of data integrity and erases allredundant data sectors. Depending on the result of the verificationprocess, the system may elect to retain the original set of datasectors, or may retain one of the duplicate sets of data sectors,including the relevant header information and association data. Once thedisk has been erased, the disk may be operated normally. The systemwhere the media disk is integrated then utilizes the selected set ofdata sectors as a basis for further operations on the disk, includingdata storage to the disk.

[0241] Head Stack Failure Detection and Handling

[0242]FIG. 18 illustrates one possible implementation of the presentsystem. From FIG. 18, the media disks of the present system areoptionally encased by a shrouding arrangement, shown as two shrouds, andan acoustic sensor 1801 is mounted on a positioner arm 1802 proximatethe disks. The acoustic sensor is employed to detect the noise producedby one or more heads that come in contact with one or more correspondingdisks upon the occurrence of or in advance of a head crash. When a headcrash is imminent, it is understood that the acoustical emissions by thedrive may take on certain abnormal characteristics, and in the presenceof these abnormal characteristics, it is preferable to remove the heador heads from the disk. Impending head crashes may produce differentcharacteristics in different drives and may even vary under differentcircumstances within a single drive. Unusual or abnormal circumstancesmay include, but are not limited to, high frequency variations orripples. With respect to sensing such abnormal circumstances or the,existence of a head crash, it is to be specifically understood that theacoustic sensor may be located in an alternate position from that shownin FIG. 18, such as on the e-block, on a disk cover, or otherwise, andmore than one such sensor may be employed. Location of the acousticsensor as close to the head as physically possible and practicable isone possible way to locate the sensor. Sensor location will depend on avariety of factors, including but not limited to physical constructionof the servowriter, placement of the heads, and associated acousticalissues.

[0243] During normal operation, the head reading from or writing to adisk is displaced in physical proximity of the disk. The head and thedisk are normally not in direct physical contact, but are operationallycoupled. For example, for a magnetic disk, a head flies relatively closeto the surface of the disk reading from, or writing to the media diskvia magnetic fields that propagate across the physical gap between thehead and the disk.

[0244] When a head crashes, possibly as a result of a mechanical orpower failure, the head may contact the corresponding disk producing acharacteristic noise. While a disk failure may create sound waves havingvarying characteristics, the noise is typically characterized byfrequencies and amplitudes in particular ranges. Certain pending headcrashes may also exhibit frequency or amplitude abnormalities. Theimplementation of the invention described herein utilizes an acousticsensor 1801 to detect this characteristic noise. The noisecharacteristic to a head crash exhibits a certain sound intensity andoperates within a certain frequency spectrum. This implementation of theinvention distinguishes the noise characteristic to a head crash fromother noises that may otherwise occur in the system by determining thenoise in the system, detecting amplitude and frequency levels, andindicating when those amplitude and frequency levels fall outside anexpected range or within an undesirable range. The acoustic sensor andassociated electronics only react to sound whose intensity exceeds acertain threshold and whose frequency spectrum matches the frequencyspectrum characteristic to a head crash.

[0245] From FIG. 18, media disk 1805 has head 1803 operating above andin association therewith. Positioner base 1802 has acoustic sensor 1801affixed thereto, and positioner base 1802 is adjoined to head 1803 viapositioner arm 1804. Acoustic sensor 1801 is electronically linked tocomputing device 1806, which may be any electronic device capable ofdiscriminating between signals, dynamically computing values in realtime, and transmitting command values to a voice coil and/or voice coilmotor, such as a digital signal processor. The computing device 1806determines whether the sound intensity is within an expected range orwithin an unexpected range and commands the VCM (not shown) to lift thehead 1803 from the disk 1805 under failure conditions.

[0246] The sound intensity associated with the noise produced by a headcrash depends on various factors, including the physical characteristicsof the disk and head. The system, via the acoustic sensor 1801 and theassociated electronics, only reacts when the intensity of the sounddetected exceeds a certain threshold or is within an undesirablethreshold range. A value of this threshold may be determinedexperimentally for a particular combination of head and disk, or may bedeveloped analytically. As may be appreciated, a disk failure due to,among other causes, a broken disk, produces a high amplitude sound. Inother circumstances, such as a power failure, a failure is indicated byan absence of sound. Normal operation of disks, particularly inservowriting and certification, is a constant speed rotational sound,sometimes called a “whirring” or “whizzing” sound. These tend to beconstant sounds, unlike a traditional hard drive sound that operates infits and starts depending upon the function performed by the hard diskdrive. In hard disk drive operation, the disk may not spin for a periodof time and then spin for an extended period of time. Theservowriter/certifier hardware system, by contrast, may be either on oroff for an extended period of time, and thus noises outside the expectednorm may be considered a system failure.

[0247] In one aspect, the acoustic sensor has a relatively lowsensitivity such that it only detects noise above the threshold. Inanother case, the acoustic sensor detects a wider range of soundintensities, but software and/or hardware logic coupled to the acousticsensor responds to the system when the sound intensity detected by thesensor is below a particular threshold. Software and/or hardware logiccoupled to the acoustic sensor may be configured to respond to a rangeof sound thresholds.

[0248] The frequency spectrum associated with the noise produced by ahead crash also depends on the physical characteristics of the disk andhead, among other factors. The system only reacts when the frequencyspectrum of the sound detected matches a certain frequency spectrumsignature. This frequency spectrum signature may be determinedexperimentally for a particular combination of head and disk or disks,or may be developed analytically. In one case, the acoustic sensor has aparticular spectral sensitivity such that it only detects noise whosefrequency spectrum matches the frequency spectrum signature. In anothercase, the acoustic sensor detects a wide range of frequencies, butsoftware and/or hardware logic coupled to the acoustic sensor suppressesresponse of the system when the frequency spectrum detected by thesensor does not match the appropriate frequency spectrum signature.Software and/or hardware logic coupled to the acoustic sensor, possiblyincluding frequency filtering logic, may be configured to respond to arange of spectral frequencies and suppress other frequencies.

[0249] The intensity and frequency spectrum of the sound detected by theacoustic sensor may also depend on the proximity of the sensor withrespect to the point of contact between the disk and the head. In aparticular implementation, the acoustic sensor is disposed on the armsupporting the head, in physical proximity to the head. In anotherimplementation, the acoustic sensor is located on the e-block, furtheraway from the head.

[0250] In one implementation, multiple acoustic sensors are employed todetect head crash in a multiple head, multiple disk environment. In thisimplementation, multiple heads read and/or write information to multipledisks substantially simultaneously. There may be more than one headoperationally coupled to each disk. Further, there may be more than onehead coupled to each VCM-driven arm, possibly coupled via actuators, andthere may be more than one arm operating on each disk. In thisimplementation, multiple acoustic sensors may be disposed throughout thesystem to detect head crashes that may occur at any point in the system.Each acoustic sensor and associated logic may correspond to a particularhead and may be configured to ignore head crash noises produced by anyother head. Alternatively, the system may utilize information producedby a multitude of sensors to identify the head that crashed (e.g.,through triangulation and/or through a spectral and intensity soundanalysis that considers the characteristics of various disks, heads andsystem components disposed throughout the system).

[0251] If possible, in the current system and in many other systems, theacoustic sensor would be located as close to the head as possible.Physical drive characteristics limit the proximity of the acousticsensor to the disk, but such a sensor may be employed at or near thepositioner, e-block, shroud, or other points in the representativedesign illustrated herein.

[0252] In operation, once a head crash or other system failure isdetected using the sensor or sensors disclosed herein, the systemretracts the heads or otherwise moves the head or heads away from thedisk or disks as rapidly as possible. This removal of heads from disksprovides necessary space between disk and head. While the head may stillcontact the disk under certain failure conditions, such as a diskfracture or head failure, removal of the heads from the disk breaks thetypical association between disks and heads and minimizes the chance ofdamaging either. Removing heads from the disk is a normal circumstanceof media servowriting, and thus the system operates in a known mannerwhen removing heads from the disks. Under one condition, a power failurecauses the system to rectify the voltage available from the spindle andthat voltage is applied to the voice coil, or alternately directly tothe voice coil motor, which moves the head or heads away from the mediadisk or disks. In operation, a ramp type structure is moved by the voicecoil motor to contact head holding apparatus and lift the head.

[0253] In other words, in one implementation, the invention utilizes thespindle as an electrical power generator to retract the heads off thedisk.

[0254] In this implementation, the system utilizes a relay to detect apower failure. In one case, the relay detects when the electricalvoltage at a particular point decreases below a certain threshold. In aparticular case, this threshold is eight volts.

[0255] Upon a loss of power, the spindle continues to rotate due to itsangular momentum. The mass of the spindle and other subsystemsmechanically coupled to the spindle is relatively large, such that theangular momentum of the spindle system is correspondingly large. Uponloss of power, the spindle continues to spin for a significant period oftime.

[0256] The invention exploits the angular momentum of the spindle byutilizing the spindle as an induction power generator. Inertial rotationof the spindle induces electricity in a coil. This coil may besubstantially stationary with respect to the spindle, and thereforerotate with the spindle, or may be stationary with respect to the baseof the spindle. In one case, the coil is part of the electrical motorthat engages and rotates the spindle under normal operating conditions.

[0257] The electrical power produced by the spindle is rectified and isemployed to operate servo systems that may retract the heads off thedisk. In one aspect, the electrical power produced by the spindle isdivided into two components: a first component operates a voice coilmotor that retracts the heads off the disk, while a second componentoperates a motor that moves a ramp that mechanically engages the headsin a preferred resting position.

[0258] The present invention may apply to a single head operating on acorresponding disk, to multiple heads operating on a singlecorresponding disk, or to multiple heads operating on multiple disks.

[0259] As an alternative to the foregoing, the system may determine thata pending crash is imminent or has occurred if vibrations occur withinthe spindle. In such an arrangement, the spindle is monitored with avibration sensor to detect spindle movement, and abnormal readings infrequency, amplitude, or intensity may be employed to remove the headsfrom the disk in certain circumstances.

[0260] This aspect of the invention has been outlined in the context ofa rotating spindle. In an alternative implementation, the invention mayalso apply to a medium in linear motion (e.g., conveyor belt-type ofsystem). In such a system, failure causes operation of a ramp thatmechanically engages the heads in a preferred resting position.

[0261] Media Shroud

[0262] 1. Multiple-Disk Shroud.

[0263] One implementation of the invention disclosed herein provides amultiple-disk shroud comprising a left baffle shroud and a right baffleshroud. From FIG. 19, the left baffle 1901 comprises a plurality ofindividual left baffle cavities 1902 a-n corresponding to disks arrangedin a stacked formation. Each individual left baffle cavity 1902comprises an opening or slot that fits around the media and is adaptedto partially receive a corresponding media disk, thereby partiallyenclosing the disk. In a particular embodiment, each individual leftbaffle cavity 1902 extends substantially to the center of thecorresponding disk, thereby enclosing substantially half of the disk.The distances between the inner planar surfaces of each left baffleshroud and the corresponding planar surfaces of the corresponding diskare preferably small. In a particular case, these distances areapproximately 10 mils, or {fraction (10/1000)} of one inch. Constructionof this aspect of the current invention therefore comprises a series ofseparating walls, wherein the separating walls create the cavities 1902in the baffle shroud.

[0264] As may be appreciated by those skilled in the art, the number ofleft baffle cavities or openings generally corresponds to the number ofmedia disks in the arrangement or disk stack, such that the existence offive disks in the stack dictates a baffle shroud or shrouds with fivecavities, while the existence of eleven media disks in the stacksuggests eleven left sets of cavities in each baffle shroud. The numberof left baffle cavities is generally related to the number of availabledisks or media that may be employed, rather than the actual numberemployed. In the previous example, if the spindle or disk holding deviceis capable of holding five disks but is only fitted with three disks,the number of cavities will be five. The foregoing is meant by way ofexample and not as a limitation.

[0265] The media disks are disposed in substantially parallel planes andmay spin around a common axis that is substantially normal to the planesof the media disks. The disks are operationally coupled to correspondingheads that may read and/or write data to the disks.

[0266] The left baffle 1901 may be translationally coupled to the frameof the servowriter such that the left baffle 1901 may pivot intophysical proximity of the media disks. In one embodiment, the leftbaffle 1901 is not directly coupled to either the media disks or theread/write heads, and may translate independently of the disks andheads. Upon translating proximally to the disks, each of the individualleft baffle shrouds 1902 a-n partially encloses a corresponding disk,thereby controlling air flow around the disk as the disk spins at arelatively high velocity.

[0267] In a further aspect of the present invention, a right baffle 2001as illustrated in FIG. 20 is analogous to the left baffle 1901 describedabove and comprises a plurality of individual right baffle cavities 2002a-n corresponding to the number of media disks that may be loaded on thespindle. The structure and functionality of the right baffle aresubstantially the same as the structure and functionality of the leftbaffle, although certain differences exist. One such difference betweenthe left and the right baffles 1901 and 2001 is that the planardimensions of the right baffle shrouds in this aspect of the inventionare smaller, such that each right baffle shroud receives and protects asmaller portion of the corresponding disk. In a particular embodiment,each right baffle shroud encloses substantially a quarter of thecorresponding disk. In a related embodiment, each left baffle shroud andthe corresponding right baffle shroud cooperatively enclose anon-insubstantial portion of the disk, in the aspect illustratedapproximately {fraction (3/4)} of the corresponding disk. The remaining¼ of each such disk is essentially covered by one or more heads and/orother related hardware.

[0268] Other specific dimensional characteristics are available for theleft and right baffle, as may be appreciated by one of skill in the art.The function and purpose of the shrouding arrangement is to cover asmuch media disk surface as reasonably practicable while at the same timeallowing reasonably free access by the read and write heads to the mediadisks. Alternate designs include, but are not limited to, use of asingle shroud similar to the left shroud covering approximately half themedia surface, and use of a shroud covering approximately half thesurface similar to the left shroud 1901 and a larger or smallerdimension right shroud than that shown. Dimensions of the shroud orshrouds are dictated by various factors, including desired rotationspeed of the disks, physical dimensions of the positioner arm or arms,amount of media disk access required, and disk holding considerations,such as spindle, chuck, and other holding mechanism dimensions. By wayof example and not limitation, the spacing between the disks and theshroud or baffle hardware may be as small as on the order of 10 mils andpossibly lower, such as 9 or 8 mils.

[0269] When engaged in an operational position in the configurationillustrated in FIGS. 19 and 20, the right baffle 2001 may be disposedsubstantially opposite to the left baffle 1901 with respect to thespinning axis of the disks. The translating directions of the left andright baffles 1901 and 2001 are also opposite, with the left baffle 1901approaching the disks from the left direction and the right baffle 2001approaching the disks from the right direction. Further, unlike the leftbaffle 1901, which may translate independently of the heads, the rightbaffle 2001 is mechanically coupled to the read/write heads andassociated positioner in one aspect, such that the heads and the rightbaffle are disposed on the same arm. In this aspect, when the heads areengaged in a functional position by the voice coil motor (VCM), theright baffle 2001 is substantially simultaneously disposed in anoperational position. Subsequently, during normal operation, the headsmay move with respect to the disks and the right baffle 2001 whilereading and/or writing to the disks, but the individual right baffleshrouds 2002 a-n remain substantially stationary with respect to thecorresponding left baffle shrouds 1902 a-n and the spinning axis of thedisks.

[0270] It is to be understood that the foregoing represents a singlespecific design of the present invention and is not meant to be limitingto the design shown. Translating is not necessarily required, and forexample the shrouds may be fixed in position, disks may be rotated intothe shroud using a movable spindle, and either one, both, or neithershroud may interact directly with the positioner, VCM, and other systemhardware. The design must, at a minimum, provide a level of coverage orenclosure of the media disks and decrease the risk of windage disruptingthe interaction between head and disk.

[0271] In one aspect of the current invention, the left baffle 1901 andthe right baffle 2001 are constructed from aluminum. Alternatively, theleft baffle 1901 and/or the right baffle 2001 may be constructed fromplastic. Other materials may be employed while within the scope of thepresent invention, provided the materials provide adequate strengthcharacteristics and operate to minimize the risk of turbulent flow inthe arrangement selected. Thus materials such as aluminum and/or plasticmay be used, but these materials are neither required nor exclusive forconstructing the inventive baffle arrangement shown herein.

[0272] In a particular implementation, the left and/or right baffles1901 and/or 2001 may comprise one or more vacuum ports or inlets (notshown in the illustrated aspect but known to those of skill in the art)that may be utilized to remove debris or particles located in proximityof the spinning disks. Such debris is typically found in the form ofsmall particles, and such small particles may inhibit performance of thedisk stack. The inlet operates in connection with a vacuum pump tointake or vacuum air and particles from the shroud arrangement. Theinlets may be located at each baffle, or at one baffle, and may span allchambers of the baffle, a single chamber of the baffle, or anyintermediate number of chambers. The purpose and functionality of theinlet arrangement is to remove unwanted particles and provides a meansto reduce the quantity of ambient particles contacting disk surfaces inthe multi disk arrangement. The inlets or vacuum ports may be a singlesmall diameter hole located atop or on the side of the baffle, oralternately a long sealed opening on the side of the baffle to affordaccess to each disk and chamber or cavity. Other vacuum port or inletshapes and configurations may be employed while still within the scopeof this aspect of the invention.

[0273] While varying dimensions may be employed, particularly of theshroud, baffle, baffle Alternate views of the baffles are illustrated inFIGS. 22 through 27. FIG. 22 is a top cutaway view of the left baffle.FIG. 23 is a side cutaway view of the left baffle. FIG. 24 is a bottomview of the left baffle. FIG. 25 is a side view of the right baffle.FIG. 26 is an alternate perspective view of the right baffle. FIG. 27 isa bottom view of the right baffle.

[0274] 2. Clock Head Shroud.

[0275] Another embodiment of the invention provides a shroud that mayprotect a media disk while a clock head reads or writes data from thedisk. The shroud of this aspect of the invention is presented in FIG.28. The clock shroud 2801 encloses the head at close proximity to thedisk substantially completely, but comprises a number of apertures, suchas first relief cut 2802 and second relief cut 2803, that permitintroduction and withdrawal of the clock head and/or of other devices.Such relief cuts are beneficial in certain circumstances but are notrequired as part of the present invention; rather, the important aspectof the invention is to provide a shroud or covering that covers the headand decreases the amount of windage encountering the head and reducesrisk of disruption of the head-media disk interaction. In the designshown, additional apertures located in the shroud permit disposition ofcertain devices, such as a motor. The use of the clock shroud enables amore accurate clock and timing arrangement for the system, minimizesinterference between the clock head and the disk, keeps certain data,such as servo pattern data phase coherent, and minimizes vibration. Theclock head sits in the notch illustrated in FIG. 28. FIG. 29 is a topview of a clock shroud that may be employed in association with thecurrent invention.

[0276] Head Mounting Design

[0277] A further aspect of the present design is employed in connectionwith the heads writing to and reading from the media in theconfiguration presented above. More particularly, the present designincludes a system and method for mounting the heads to relevanthardware, such as an assembly or holding device, positioner arms and anE-block, so that the heads can be removed and replaced in a moreefficient manner than previously known.

[0278]FIG. 30 presents one rotary voice coil motor design 3001 that maybe employed in a media track writer or servowriter as shown above,wherein the voice coil motor is used to drive the head positioner andthe heads located thereon. The voice coil motor design 3001 is abalanced torque design having twin coils 3002 and 3003 placed onopposite sides of a central pivot. The rotating portion of the voicecoil motor is suspended on two high precision preloaded ball bearings(not shown), and includes the coil housing 3101 of FIG. 31, two coils3201 shown in FIG. 32, scale holder 3301 and shaft 3302. The shaft onthe scale holder 3301 and shaft 3302 assembly, including dowels 3303,3304, and 3305, are used to guide and align the scale holder to the FIG.34E-block positioner arm assembly 3401. The shaft 3302 fits into cavity3402 in E-block positioner arm assembly 3401, with coarse angularalignment established by crosswise dowel pin 3303 and final angularalignment performed by smaller dowel pin 3304. E-Block 3403 is attachedto the remainder of the E-Block positioner arm assembly 3401. Thissmaller dowel pin 3304 is inserted between scale holder 3301 and theE-block positioner arm assembly 3401. A standard wing nut, not shown,fastens the E-block positioner arm assembly 3401 to the scale holder3301 and shaft 3302. This wing-nut attachment of E-block and headassembly provides for rapid loosening of the wing nut, releasing theshaft, removing the shaft, and disengaging the E-Block positioner armassembly 3401 from the rest of the media writer. It is desirable toperiodically replace the head assembly to address normal wear and tearduring servowriting or damage to one or more heads resulting from faultydisks while retaining the assembly for future use.

[0279] With respect to the head assembly, and namely the assemblyexclusive of the head, E-Block, and positioner arms, the way the deviceis assembled during operation is as follows. Individual head-gimbalassemblies (HGAs) are attached to small mounting tabs. When assembled,the HGA may be attached to mounting tab 3501 as shown in FIG. 35, whichis then affixed to the arms of the E-block 3601, shown in detail in FIG.36. Each mounting tab 3501 is held in place on the E-block arms using asmall screw, such as a M1.2 screw, which passes through channel 3504.FIG. 36 illustrates a top view of the E-Block 3601 bifurcated by animaginary centerline. Alignment of the mounting tab and E-block 3601 ofFIG. 36 occurs using the two dowel pointed pins 3502 and 3503, which areultimately inserted into two slots 3602 and 3603 in E-Block 3601. Fromthe angle of FIG. 36, only one slot 3603 is visible. Use of the dowelpointed pins 3502 and 3503 align the tab 3501 to the arm 3606 of theE-block 3601. A tab having one or two heads may be removed from orassembled to the E-block with the installation or removal of a singlescrew.

[0280] The present apparatus obviates the need for the previous methodof “staking.” The present design uses a press fit scheme, whereby theHGA and head mount components are pressed into place and secured toother assemblies using dowels, pins, screw, wing nut, and othercomponents. Staking required mounting tab replacement or head arm orE-block after only two or three head replacements due to permanentdeformation of the boss receiving bore 3504 of the head mount. Thepresent design employs a smaller head bore 3504 than the mating boss onthe head suspension, enabling the HGA to be attached to the head mountby applying pressure, or pressing, the part and forcing the suspensionboss into the head mount bore 3504. This pressing operation allows thesuspension boss to maintain sufficient torque to allow proper headoperation during functions such as ramp load and unload of heads ontothe disks. Compared to staking, a press fit or a pressure fitting hasthe ability to impart less distortion to the interface between the HGAand the mating head mount bore, increasing the number of reuses of thehead mount tab 3501 before replacement is indicated. Since HGAdistortion is generally less than that of the mating head mount bore,head damage can be minimized by press fitting rather than staking.

[0281] An alignment and pressing fixture may be employed to assemble oneor two HGAs to a head mount. HGAs may be assembled using the devicesshown in FIG. 37. In practice, the head mount is located within thecenter section 3702 while one or two HGAs are affixed to the head mountdepending on the application. HGAs are sandwiched between the leftsection 3701 and the head mount fixedly positioned within center section3702, and/or the head mount fixedly positioned within the center section3702 and the right section 3703. The heads are then aligned with andaffixed to the head mount tab, which is thereafter assembled on theE-block.

[0282]FIG. 37 illustrates an exploded view of the three sections and theassociated hardware used to prepare the HGA or head assembly and mountfor receiving a read/write head. In FIG. 37, the head mount tab (notshown) is mounted to the head assembly tool 3704. The center section isused to align and mount the tab to the HGA using the aforementioned M1.2screw (not shown in this Figure). Heads are placed between the press-fitjaws of left and right assembly tool parts 3701 and 3703, between thoseassembly tool parts and the center section 3702, and are aligned usingthe HGA support 3705. The right head assembly tool part 3701 may beforced toward the center section 3702 using a vise or other clampingdevice, and the HGA bosses are press fit to the head mount tab bore. Thehead mount tab is aligned using the HGA support 3705 and alignment toolpins 3706 and 3707. The pins may be a straight or stepped pin to providenecessary support and alignment for the tasks outlined below.

[0283] Each of the assembly tool parts, left section 3701, centersection 3702, and right section 3703 have slots cut through the materialto provide limited lateral flexibility. The flexibility enables the toolto be used for a head to be assembled on either side of the head mounttab, or both sides may be assembled at once.

[0284]FIGS. 38A, 38B, and 384C show details of the three assembly toolparts, left section 3701, center section 3702, and right section 3703.These are representative of one possible implementation, and otherimplementations may be employed while within the scope of the presentinvention.

[0285] Assembly of the system is shown in FIGS. 39-43. FIG. 39illustrates a high precision vise 3901, the two alignment tool pins 3706and 3707, the assembly tool 3902 comprising left section 3702, centersection 3703, and right section 3704, the head assembly 3803, and toolsfor performing the head assembly. ESD protection may be employed duringhandling operation, and the work may be performed under a clean hood byan operator with gloved hands. The assembly tool may be constructed fromany appropriate material, including but not limited to stainless steel,such as a cold rolled type 302 or 304 stainless steel. Other materialsmay be employed that provide sufficient holding, wear, and strengthcharacteristics, among other advantageous aspects.

[0286] Head arm mount 3501 is inserted into the assembly tool 3902. Thehead assembly tool 3902 is maintained within the precision vise 3901grasping the base of the tool 3902, thereby applying a level of pressureor tension to the assembly tool, but not so much as to restrict movementof the upper section of the tool sections. The center, right, and leftsections of the assembly tool 3905 may be spread such that the head armmount may be inserted in the gap and the pins of the head arm mountaligned into the center section 3703 of the assembly tool 3902.Spreading may occur by various means, including using the operator'sfingers to separate the left, center, and right sections of the assemblytool 3902. The M1.2 screw is then tightened, thereby wedging the sidesof the head arm mount 3501 within the center section 3703 of theassembly tool 3905. The operator or a machine may then pick up the headassembly, spread the outer members of the assembly tool and gentlyinsert the head assembly between two of the sections, such as the leftsection 3702 and the head arm mount 3501. The staking boss (not shown)of the head assembly 3903 may be approximately aligned with the upperhole of the head arm mount 3501.

[0287]FIG. 40 presents a side view of a sample head assembly 3903, heldwith tweezers by an operator. This sample head assembly is onlyrepresentative of the types of head assemblies that may be employed, andthe head assembly shown has the ability to maintain the drive head 4002at the top end in the orientation shown and has various openings whichenable the assembly and alignment described below. It is to beparticularly noted that other head assembly designs may be employedwhile still within the scope of the present invention.

[0288] In initial operation, the head arm mount 3501 is located withinthe assembly tool 3905, namely center section 3702. In an orientationwhere the center section spacing gap is positioned upward, the pins 3502and 3503 of the head arm mount 3501 are oriented downward and the headarm mount 3501 is pushed down into the center section 3702. A screw isinserted through channel 3504, such as an M1.2 screw, to apply pressureto the sides of the head arm mount 3501 and fixedly mount the head armmount 3501 to the center section 3702. FIG. 41 illustrates a head armmount 3501 positioned against the head assembly 3903 within the assemblytool 3905. FIG. 41 further illustrates insertion of a pin 3707, such asa straight 0.8 mm diameter pin, through the upper slots of the assemblytool 4103 and through a tooling pin hole in the head assembly 4103.

[0289] In certain circumstances, the head assembly may be repositionedso that pin 3707 can engage the tooling hole in the head assembly 3903.FIG. 42 illustrates insertion of pin 3706, such as a stepped 2.13 mmdiameter pin, into a lower hole 4201 in the assembly tool 3905. The pin3706 may be inserted carefully such that it passes through the headassembly 3903. An operator or machine may at this point inspectalignment of the head assembly 3903 within the head arm mount 3904.Inspection may occur in any available reasonable manner, including butnot limited to a low power stereo inspection microscope. If alignment isacceptable, the pins 3706 and 3707 may be removed from the alignmenttool. Spring pressure from the assembly tool 3905 in many circumstanceswill keep the head assembly aligned to the head arm mount 3501.

[0290] The upper edge of the alignment tool 3905 may then berepositioned within the vise 3901 as shown in FIG. 43. A relativelysmall section of the alignment tool 3905 may be inserted into the vise3901, such as less than 10 mm. A relatively small amount of pressure isthen applied by tightening the vise 3901, thereby press fitting the headassembly 3903 into the head arm mount 3904. The screw may then beremoved from the head arm mount 3501 and the head assembly press fittedto the head arm mount 3501 may be removed from the assembly tool.

[0291] Other implementations of the press fitting method described aboveare within the scope of the present invention, and the foregoingdescription, as with all descriptions of particular design aspectsherein, is not intended to be restrictive or limiting.

[0292] Disk Biasing

[0293] An aspect of the present invention provides methods and systemsfor controlling disk position on a central hub or chuck during servotrack writing and/or reading. The disk position control may occur priorto installation into a Hard Disk Drive. The disk biasing methods andsystems disclosed herein may be applied to single or multiple disks,require minimal or no operator intervention, and provide a repeatableway to control eccentric placement of servo information onto the disk.

[0294] One aspect of the MTW that is particularly noteworthy is themechanical clearance between the disk inside diameter, and the hub orchuck outside diameter, namely the disk opening and the hub that fillsthe opening. A significant clearance dimension is necessary to enablefast and reliable disk installation on and off the hub and toaccommodate disk and hub manufacturing tolerances. Excessiveeccentricity, or servo track “runout”, can cause servo capture andperformance problems for the HDD, in that the head can be mislocatedabove the disk and can run outside a track, or begin in one track andend in another.

[0295] One way to deal with this excessive eccentricity aspect of amedia track writer is to have a mechanism to “center” the disk on thehub at disk installation. Centering the disk typically may requireprecise and expensive fixturing to achieve reasonable accuracy. Another,often less expensive, way to address excessive concentricity is to“bias” the disk ID against the hub OD in a controlled manner so thatthis same “bias” can be applied when the disk is eventually installedinto an HDA, thereby controlling the eccentricity rather than allowingtolerances to vary unpredictably to significant error levels. Anecessary part of this process is maintaining and/or determining thebias direction and circumferential point where the bias is applied. Suchuse of bias direction and circumferential point may be accomplished bymarking the disks or by handling the disks in a controlled andrepeatable way.

[0296] To consistently bias a disk, an embodiment of the invention canapply biasing force to the disk OD, usually by using a very precisefixture or tool. By alternately biasing disks against the HDA spindlehub in opposite directions using “V” shape devices to push on the diskOD, rotational unbalance forces can be minimized. Typically, these “V”shape devices are placed on either side of the disk and spindle stack,such that half the disks are biased in one direction and the other halfbiased 180 degrees in the opposite direction. This way, for stacks ofeven numbers of disks, first order disk unbalances can be minimized.These “V” shape blades may be made slightly compliant to compensate fordisk, spindle hub, and biasing tool mechanical tolerances, either byusing a compliant material or some mechanical compliance, such as aspring type mechanism. The vertical axis of the biasing tool used toapply the “V” shape blades may be precisely aligned to the spindle hubaxis to consistently bias the disks in the appropriate direction at alllocations in the disk stack. Further, biasing of disk spacers may beemployed using OD biasing.

[0297] An embodiment of the invention biases the disks using the diskID. In this case, biasing forces are applied in an outward radialdirection to the disk ID at one or more points, such as two points, toforce the disk in a known direction against the spindle hub. The biasingforce can be applied in various ways, including but not limited to usingair pressure to automatically bias disks in the stack in the requireddirection. Two, small, piston-like devices within the spindle hub may beused to apply a radial vector sum force in a known direction to eachdisk. By arranging the piston-like devices in a pattern, forces can bedirected in any direction for each disk. The simplest pattern would be180 degree opposite force vectors for each disk, such that the netrotational unbalance force for an even number of disks, assumingidentical disks, would be zero. Even numbers of disks ensure dynamic aswell as static force balance. For each disk, each group of twopiston-like devices is arranged in a manner to provide a vector sumforce in a known direction.

[0298] According to an embodiment, an arrangement that facilitates themanufacturing process, comprises two pistons radially oriented withrespect to hub axis and spaced an angle apart. Although many angles willwork, the preferred angle for manufacturing is 90 degrees. This angleprovides a vector sum of 1.414 times the force generated by each piston,in a direction half-way between the pistons, or in this case, 45 degreesfrom either piston, directed radially outward. In addition, lateralforces are generated by each piston, and these lateral forces tend toforce the disk laterally until a force balance exists on the disk.Friction related forces may also exist. A friction force has a tendencyto oppose the biasing force, irrespective of the direction of thebiasing force.

[0299] The directional accuracy with which the disk will be biaseddepends upon the ratio of the magnitudes of the friction force to thebiasing force. It may be beneficial in certain circumstances to minimizefriction and maximize the biasing forces for each disk. Friction betweendisks and disk spacers can be minimized by using special platingprocesses on the spacers. For example, hard nickel plating or nickelplating with embedded Teflon particles have demonstrated low frictioncoefficients with most disk surfaces. Other coatings and/or materialscan be used as well.

[0300] One implementation of the present aspect of the design includes afour disk chuck assembly with integral disk biasing. Disks are stackedonto a chuck and spaced vertically using a spacer. Once the stack isassembled and biasing done, the stack is clamped together using a topcap. Biasing is accomplished by use of pressurized air or other gas suchas nitrogen, prior to clamping. Disk clamping is performed with a singlescrew, although alternate designs may utilize vacuum or other mechanicalclamping means. Air or other gas used for biasing is introduced throughthe bottom base of chuck, distributed by a shaft, with biasing forcesgenerated by a ball and orifice housing assembly. If both air pressureand vacuum is used (first for biasing then for clamping), internal checkvalves within chuck body direct air or vacuum to the appropriate areasas necessary. The biasing forces generated by the pair of ball andorifice housing assemblies are self balancing via use of a seriescombination fixed and variable orifice within the assembly.

[0301] The design resembles air-bearing systems where self balancingforces are generated by use of a fixed orifice in series with a variableorifice, with the air pressure between the two orifices used to providea lifting or noncontact bearing action. In an air bearing, the variableorifice is nearly always created by one member of the bearing movingwith respect to the other. In this biasing design, the variable orificeis created between the moving ball which contacts the disk I.D. and theangled ball seat within the housing. Pressurized air flows first throughthe fixed orifice, which is in the order of 0.010 inches diameter, thenthrough the variable orifice. The air pressure between the 2 orificesacts on the ball to create a force directly proportional to thatpressure. As the ball moves outward, the pressure falls, reducing ballforce. As the ball moves inward, thus reducing the area of the variableorifice, the pressure increases, increasing the ball force. With two ofthese ball and orifice housing assemblies arranged so that radiallyoutward forces are applied to a disk at a fixed angle between thedevices, a vector sum force can be applied such that the direction iscontrolled. Use of the fixed/variable orifice set devices provides aself-balancing action such that the force vector always applies a forcevector to the disk such that the disk is forced or “biased” against thechuck body in a specific direction and point on the chuck. That contactpoint between disk and hub is approximately 180 degrees opposite the twoball orifice housing piston devices.

[0302] By alternating the direction, e.g. 180 degrees, in sequence foreach disk, the disks can be forced outward in alternating directionssuch that half the disks are biased one way and half are biased theopposite direction. This alternating of bias direction compensates forfirst-order unbalance effects due to the disk centers being displacedfrom the chuck rotational center.

[0303] The described disk ID “biasing” method is but one of manypossible detail configurations wherein changes in the design would notprovide a fundamental difference from the basic concept describedherein. Specifically, the number of disks, disk spacing and anglesbetween the pair of ball and orifice housings can be easily modified toa near infinite number of combinations without affecting the fundamentaloperation of the biasing concept. Also, the pushing elements can beother than ball shapes, including but not limited to other piston-likedevices. In addition, while a fixed orifice in combination with variableorifice is believed to have higher accuracy of final vector direction,it may also be possible to simplify the design further, by using pistonsor balls alone within a simple radial bore, provided the forces arelimited so that no permanent disk ID surface deformation, “brinneling”,or other damage occur.

[0304] Locking Cap

[0305] A further aspect of the present invention includes a specificmechanical aspect used to hold one or more of the disks in place in themedia servowriter. An aspect of the present system includes certainaspects designed to facilitate maintaining disks at high rotationspeeds. FIG. 44 illustrates a general view of one aspect of the device.FIG. 44 illustrates the disk maintenance design in a locked downconfiguration. A closer view of the inner elements of the design ispresented in FIG. 45. The device includes a top cap 4401, a centralchamber 4402, an annular compression spring 4403 and 4404 designed topull the cap downward, and a set of ball bearings 4405, two of which arevisible in these views, abutting the central core 4406 of the cap 4401.To unlock the device, the cap 4401 must be released, which requiresapplication of air to the central chamber. Air is applied to the centralchamber through the bottom of the device (hub). Air pushes up thecentral cylinder and the ball bearings 4405 buttressing the central core4406 of the cap, thereby applying tension to the compression springs4403 and 4404. When the ball bearings 4405 and the chambers in whichthey are located rise to a level proximate the upward sloping walls inthe interior of the chamber, the ball bearings 4405 slide outward alongthe upward sloping walls 4407 and out of the way of the central core4406 of the cap 4401. With the ball bearings 4405 out of the way, thecap 4401 can be readily released and disks 4410 either loaded orunloaded. In lieu of using air to engage and release the mechanism andcap 4401, a pushrod 4410 may be employed to push the central core upwardand release the cap.

[0306]FIGS. 46 and 47 illustrate the cap in released position with theball bearing and cap core in released position. Application of the cap4401, specifically locking the cap down, requires removing air pressurefrom the interior of the cap, whereupon the central chamber slidesdownward and the ball bearings re-seat in the sloping holes and lockdown the cap. Most of the components illustrated in these drawings arefashioned of metal, while the cap may be fashioned of a hardenedplastic. Any materials may be employed that satisfy the engagement andrelease aspects and functionality described herein, and the central coreand other exterior components, for example, may be fashioned of steel,nickel, or any other strong metal.

[0307]FIGS. 46 and 47 illustrate the ball bearings 4405 after havingrisen up to meet the chamber inner walls. The second figure is a closeup view of the first figure. FIGS. 46 and 47 represent an alternativeconstruct having larger compression springs and a larger interiorchamber. The present design uses six ball bearings with six innerconical-shaped passages in the ball bearing set 4405. More or fewer ballbearings may be used. Alternate sloping of the channels where the ballbearings sit or the inner chamber walls which receive the ball bearingsmay be employed, as long as depressurization causes a release of the capand pressurization holds the cap in place.

[0308] The present aspect of the system may be employed in a hard diskdrive employing multiple disks, such as a servowriter and/orcertification system verifying multiple disks, or in any otherapplication requiring use of multiple fixed media, such as computerdisks.

[0309] Multiple Finger Clamp

[0310] An additional aspect of the present system provides systems andmethods for holding a hub, specifically a hub of a disk stackingcylinder employed to hold multiple disks during disk servowriting andcertification. Previously available hub holding devices used some typeof mechanical “jaws” that gripped the exterior of the hub and/or thenotch formed between the hub and the main cylinder. The jaws were formedof some type of metal and were metal pieces used to pin the hub down andhold it in position by applying pressure to the upper side of the hub.These jaw-type locking devices tend to be imprecise in holding the hubor other cylindrical piece. At significantly high RPMs, such as inexcess of 10,000 to 20,000 RPMs, centrifugal force works to pry thesedevices open, and many jaw type devices are pried open or move the pieceas a result of high forces applied thereto. This prying tends to damagethe hub and/or maintaining device and is generally unacceptable. Thusthe previous devices could be characterized as easily pried open, withpoor repeatability, and highly subject to movement of the piece.

[0311]FIG. 48 illustrates one aspect of the present design. The lowestpiece is the spindle 4801, to which the chuck mounting plate 4802 isbolted. The central piece of the chuck mounting plate 4802 is thespindle 4803. The piece surrounding the chuck mounting plate 4802 andengaging the hub 4804 is the chuck clamp 4805. This design isair-actuated by passing air upward through the spindle and around thechuck mounting plate 4802. When air is applied, such as at a pressure of60 psi, the chuck clamp 4805 rises and the hub 4804 can be removed fromthe clamp due to the set of fingers 4806 at the top of the clamp 4805,releasing the grip on the hub 4804. When air is applied, the Bellvillespring 4807 collapses, and the central chuck clamp 4805 rises upward inthe orientation shown, and releases. The “fingers” 4806 on the exteriorflex and permit a close grip under ambient conditions. In other words,when the machine fails, it defaults to the gripped position shown inFIG. 48. The circles in the central chuck clamp are O-rings 4808 thatprovide air seals when in operation. The application of air pressure andthe upward releasing push with the finger configuration shown enablessufficient clearance to “grasp” the hub 4804. The design shown has goodpositional repeatability, and the fail-safe design offers advantagesover existing designs.

[0312] All parts may be fabricated from steel or similar materialproviding the functionality described, while the fingers 4806 andassociated chuck clamp 4805 may be formed from high strength aluminum.This material affords sufficient flexibility of the fingers in theconfiguration shown while at the same time providing sufficient strengthto hold the hub 4804. The fingers 4806 and aluminum chuck clamp 4805 maybe coated with a synergistic coating that provides significantlubrisity. The chuck clamp housing may be formed from hardened steel.Again, other materials may be used as long as they provide thefunctionality and benefits described herein.

[0313] Further illustrations of the present design are shown in FIGS. 49and 50. The angles of the fingers 4806 may be altered from the currentapproximate 10 degrees shown in FIG. 45 to 5 degrees or some othernumber. Further, the present design uses six fingers, but any numbergreater than three fingers could be used with likely adequate results.The present aspect of the design may be employed in any spin devicewhere a hub or rounded end piece must be grasped accurately, such as alathe or other industrial application. The implementation illustratedherein is that of clamping a disk hub for use in servowriting and diskinspection.

[0314] While the invention has been described in connection withspecific embodiments thereof, it will be understood that the inventionis capable of further modifications. This application is intended tocover any variations, uses or adaptations of the invention following, ingeneral, the principles of the invention, and including such departuresfrom the present disclosure as come within known and customary practicewithin the art to which the invention pertains.

What is claimed is:
 1. A method for tracking and controlling mediaread/write characteristics, comprising: creating media having apredetermined expected baseline configuration; reading said media havingthe predetermined expected baseline configuration; determining whethersaid media has moved from an expected position based on the mediareading of the predetermined expected baseline condition; and correctingdata hardware based on determining whether said media has moved fromsaid expected position.
 2. The method of claim 1, wherein saidpredetermined baseline configuration comprises media organizationstructure.
 3. The method of claim 2, wherein media organizationstructure comprises data track structure and said media is a computerhard disk.
 4. The method of claim 2, wherein media organizationstructure comprises servo data track structure and said media is acomputer hard disk.
 5. The method of claim 1, wherein said determiningcomprises utilizing a non-contact radiation detection system interactingwith the media to detect alterations in the predetermined expectedbaseline configuration and hardware coupled to said media.
 6. The methodof claim 1, said media having two sides, wherein said reading comprisesreading more than one side of the media.
 7. The method of claim 1,wherein said correcting comprises determining deviations in mediaposition based on the predetermined expected baseline condition andmoving data hardware to align said data hardware with the media.
 8. Amethod for dynamically tracking and controlling errors in mediaoperation, comprising: producing an ideal disk using patterningtechnology; and utilizing a non-contact radiation detection system withsaid ideal disk to detect media movement; wherein data from the media isfed back to hardware and/or software to compensate for position errorsduring reading and/or writing to the media.
 9. The method of claim 8,wherein producing the ideal disk comprises producing a disk having datatrack structure information located thereon.
 10. The method of claim 9,wherein producing the ideal disk comprises using lithography methods.11. The method of claim 9, wherein producing the ideal disk compriseswriting tracks using at least one electron beam.
 12. The method of claim9, wherein producing the ideal disk comprises providing the ideal diskwith a media organization structure.
 13. The method of claim 12, whereinmedia organization structure comprises data track structure.
 14. Themethod of claim 12, wherein media organization structure comprises servodata track structure.
 15. The method of claim 9, wherein said utilizingcomprises interacting with the ideal disk to detect alterations in thepatterning technology and hardware coupled to said ideal disk.
 16. Themethod of claim 9, said ideal disk having two sides, wherein saidutilizing comprises reading from the two sides of the ideal disk.
 17. Amethod of dynamically tracking and controlling errors in mediaoperation, comprising: creating an ideal magnetic disk to detect mediamovement; placing said ideal magnetic disk in association with at leastone other media; monitoring said ideal magnetic disk for electromagneticvariations in media position; and correcting hardware positioning basedon said monitoring results.
 18. The method of claim 17, wherein creatingthe ideal disk comprises producing an ideal disk having disk trackstructure information located thereon.
 19. The method of claim 17,wherein creating the ideal disk comprises using lithography methods. 20.The method of claim 17, wherein creating the ideal disk compriseswriting tracks using at least one electron beam.
 21. The method of claim17, wherein creating the ideal disk comprises providing the ideal diskwith a media organization structure.
 22. The method of claim 17, whereinmedia organization structure comprises data track structure.
 23. Themethod of claim 17, wherein media organization structure comprises servodata track structure.
 24. The method of claim 17, wherein saidmonitoring comprises employing non-contact methods to detect alterationsin the patterning technology and hardware coupled to the ideal disk. 25.The method of claim 17, said ideal disk having two sides, wherein saidmonitoring comprises reading from the two sides of the ideal disk. 26.In a system for writing to at least one magnetic disk, the systemcomprising at least one head, a method for interfacing with at least onemagnetic disk comprising: creating at least one reference mediumcomprising reference data; reading reference data from the at least onereference medium using at least one head; determining relative movementbetween the reference medium and the head using reference data receivedfrom said reading; and reducing relative movement in response to adetermination of relative movement between the reference medium and thehead.
 27. The method of claim 26, wherein said interfacing comprisesreading from the at least one magnetic disk.
 28. The method of claim 26,wherein said interfacing comprises writing to the at least one magneticdisk.
 29. The method of claim 26, wherein creating comprises making areference magnetic disk and reading reference data comprises readingmagnetic reference data.
 30. The method of claim 26, wherein creatingcomprises producing a disk using one from a group comprising: patterningtechnology; lithography; and writing using an electron beam.
 31. Themethod of claim 30, wherein reading comprises one from the groupcomprising: reflecting light energy from the disk; refracting lightenergy; and transmitting light energy.
 32. The method of claim 26,wherein reducing relative movement comprises moving the spindle.
 33. Themethod of claim 26, wherein reducing relative movement comprises movingthe head.
 34. The method of claim 32, wherein moving the spindlecomprises one from a group comprising: using an air pulse to alterspindle position; utilizing a mechanical centrifugal device; varying aninternal magnetic field within an electromotor associated with thespindle; and varying an external magnetic field surrounding the spindle.35. The method of claim 33, wherein moving the head comprises one fromthe group comprising: moving a tip of an arm attached to the head,wherein each arm is jointed and has an individual actuator associatedtherewith; and moving an arm attached to the head.
 36. A method ofdynamically tracking and controlling errors on media disks, comprising:forming an ideal disk having predetermined characteristics locatedthereon; and operating said ideal disk in association with at least onemedia disk; wherein said operating comprises determining whether said atleast one media disk has moved from an expected position based onreading the ideal disk and the predetermined characteristics thereon.37. The method of claim 36, wherein said predetermined characteristicscomprise media organization structure.
 38. The method of claim 37,wherein media organization structure comprises data track structure andsaid media disks are computer hard disks.
 39. The method of claim 37,wherein media organization structure comprises servo data trackstructure and said media disks are computer hard disks.
 40. The methodof claim 36, wherein said operating comprises utilizing a non-contactradiation detection system interacting with the media to detectalterations in the predetermined characteristics and hardware coupled toat least one media disk.
 41. The method of claim 36, said ideal diskhaving two sides, wherein said operating comprises reading more than oneside of the ideal disk.
 42. The method of claim 36, further comprisingcorrecting for perceived errors, wherein said correcting comprisesdetermining deviations in media disk position based on the predeterminedexpected baseline condition and moving data hardware to align said datahardware with the media disk.
 43. A method for minimizing likelihood ofa head within a servowriting apparatus contacting a disk locatedtherein, comprising: sensing sound intensity in a predeterminedfrequency range from a first sensor positioned at a first locationwithin the servowriting apparatus; determining the existence of apending head crash based on the sound intensity; and moving an elementof the servowriting apparatus upon determining the existence of thepending head crash.
 44. The method of claim 43, wherein moving theelement causes the head to move away from the disk.
 45. The method ofclaim 43, further comprising: additionally sensing sound intensity froma second sensor positioned at a second position within the servowritingapparatus.
 46. A method of preserving disk integrity in a mediaservowriter, comprising: receiving acoustic signals; identifyingacoustic signals falling within a predetermined range; assessing theprobability signals within the predetermined range constitute a likelyfailure event; and retracting equipment within the servowriter toprevent contact between devices within the servowriter and the disk. 47.The method of claim 46, wherein said receiving acoustic signalscomprises receiving signals at a plurality of locations within the mediaservowriter.
 48. The method of claim 46, wherein said retractingequipment causes a head to move away from a disk located within themedia servowriter.
 49. The method of claim 46, wherein assessingcomprises determining whether at least one from a group of attributes isoutside a predetermined boundary, the group of attributes comprising:amplitude; frequency; and intensity.
 50. An apparatus for decreasinglikelihood of a head contacting a disk in a servowriting system,comprising: a sensor capable of detecting a presence of sound intensityat a predetermined intensity range; a computing device programmed todetermine the presence of an undesired event; and retraction apparatusfor retracting said head from said disk when the computing devicedetermines the presence of the undesired event.
 51. The system of claim50, further comprising at least one additional listening device fordetecting a presence of sound intensity at a plurality of points withinthe system.
 52. The system of claim 50, wherein the undesired eventcomprises an impending head crash.
 53. The system of claim 50, whereinthe undesired event comprises a head crash.
 54. A method of preservingdisk and head integrity in a media servowriter, comprising: receivingsound signals falling within a certain intensity range; determiningwhether the sound signals may constitute a failure event; and retractingthe head away from the disk when the sound signals are determined toconstitute the failure event.
 55. The system of claim 54, wherein saidreceiving comprises detecting a presence of sound intensity at aplurality of points within the media servowriter.
 56. The system ofclaim 50, wherein the failure event comprises an impending head crash.57. The system of claim 50, wherein the failure event comprises a headcrash.
 58. An apparatus for determining failure in connection with aservowriting system, comprising: means for detecting sounds made by theservowriting system; and means for determining whether detected soundsconstitute a servowriting system failure.
 59. The apparatus of claim 58,wherein said detecting means comprise an acoustical sensor.
 60. Theapparatus of claim 59, wherein the detecting means further comprise anadditional acoustical sensor positioned remotely from the acousticalsensor.
 61. The apparatus of claim 58, wherein said determining meansdetermine the presence of an impending head crash.
 62. The apparatus ofclaim 58, wherein said determining means determine the existence of ahead crash.
 63. The apparatus of claim 58, wherein the determining meansmonitor at least one characteristic from a group comprising amplitude,frequency, and intensity of the sounds, and wherein the determiningmeans determines the servowriting system failure when the monitoredcharacteristic performs outside a predetermined expected value.
 64. Anapparatus for controlling airflow over rotating media, comprising: atleast one baffle covering the media, the at least one baffle comprisingat least one cavity shielding at least a portion of the rotating media;wherein the at least one baffle provides the ability to inhibitturbulent flow when the rotating media rotates.
 65. The apparatus ofclaim 64, wherein the apparatus operates and rotating media rotates inthe presence of a pressure reduced from atmospheric pressure.
 66. Theapparatus of claim 64, wherein the apparatus operates and rotating mediarotates in the presence of vacuum conditions.
 67. The apparatus of claim64, further comprising a second baffle covering the rotating media,wherein the two baffles shield substantially all of the rotating mediasave for mechanical components interacting with the rotating media. 68.The apparatus of claim 67, wherein each baffle contains a plurality ofcavities, the plurality of cavities corresponding to the quantity ofrotating media able to be placed in the apparatus.
 69. The apparatus ofclaim 64, further comprising media access equipment and a second baffle,wherein said baffle, said second baffle, and said media access equipmentsubstantially shield the rotating media.
 70. An apparatus forcontrolling airflow over rotating media, said rotating media associatedwith a head positioner, comprising: a baffle arrangement shielding anon-insubstantial of the rotating media formed such that head positionerhardware has access to a non-insubstantial portion of the rotatingmedia, said baffle arrangement comprising at least one baffle havingopenings formed to enclose individual rotating media therein.
 71. Theapparatus of claim 70, wherein the apparatus operates and rotating mediarotates in the presence of a pressure reduced from atmospheric pressure.72. The apparatus of claim 70, wherein the apparatus operates androtating media rotates in the presence of vacuum conditions.
 73. Theapparatus of claim 70, wherein the baffle arrangement further comprisesa second baffle covering the rotating media, wherein the two bafflesshield substantially all of the rotating media save for the headpositioner hardware interacting with the rotating media.
 74. Theapparatus of claim 73, wherein each baffle contains a plurality ofcavities, the plurality of cavities corresponding to the quantity ofrotating media able to be placed in the apparatus.
 75. An apparatus forcontrolling airflow over rotating media, said rotating mediaintermittently being in contact with at least one head, said at leastone head being associated with head maintaining hardware, comprising: ashroud having at least one relief cut for holding the at least one headand the head maintaining hardware over the rotating media, wherein theshroud tends to decrease airflow contacting the at least one head. 76.The apparatus of claim 75, wherein the apparatus operates and rotatingmedia rotates in the presence of a pressure reduced from atmosphericpressure.
 77. The apparatus of claim 75, wherein the apparatus operatesand rotating media rotates in the presence of vacuum conditions.
 78. Theapparatus of claim 75, further comprising a second shroud covering therotating media, wherein the two shrouds shield substantially all of therotating media save for the head maintaining hardware interacting withthe rotating media.
 79. The apparatus of claim 78, wherein each shroudcontains a plurality of cavities.
 80. The apparatus of claim 75, furthercomprising an additional shroud, wherein the two shrouds cover the atleast one head while allowing for free operation of head maintaininghardware and simultaneously enable reduced airflow over the rotatingmedia.
 81. An apparatus for controlling airflow over rotating media,comprising: a plurality of baffles covering the rotating media, eachbaffle comprising: a plurality of cavities, each cavity covering atleast a portion of a subset of the rotating media, wherein the baffleand plurality of shrouds tend to inhibit turbulent airflow duringrotation of the rotating media.
 82. The apparatus of claim 81, whereinthe apparatus operates and rotating media rotates in the presence of apressure reduced from atmospheric pressure.
 83. The apparatus of claim81, wherein the apparatus operates and rotating media rotates in thepresence of vacuum conditions.
 84. The apparatus of claim 81, saidplurality of baffles comprising two baffles, wherein the two bafflesshield substantially all of the rotating media save for mechanicalcomponents interacting with the rotating media.
 85. The apparatus ofclaim 81, wherein the plurality of cavities correspond to the quantityof rotating media able to be placed in the apparatus.
 86. A method forchanging a head assembly employed in a media writing device, comprising:providing a head mount assembly having a bore passing therethrough;positioning the head assembly adjacent the head mount; aligning the headassembly with the head mount; and press fitting the head assembly to thehead mount.
 87. The method of claim 86, wherein the aligning comprisespassing a first relatively narrow device through the head assembly tofix head assembly position.
 88. The method of claim 87, wherein thealigning further comprises passing a second relatively narrow devicethrough the head assembly and the bore of the head mount to align thehead assembly with the head mount.
 89. The method of claim 86, whereinsaid positioning comprises fixedly mounting the head mount to anassembly tool and locating said head assembly adjacent to the fixedlymounted head mount.
 90. The method of claim 89, wherein the pressfitting comprises compressing the assembly tool, thereby pressing thehead assembly against the fixedly mounted head mount.
 91. The method ofclaim 89, wherein said assembly tool comprises a plurality of sections,and said sections employ a spring to draw said sections together andhold said head assembly and said fixedly mounted head mount.
 92. Amethod for replacing drive heads, comprising: abutting a headmaintenance arrangement to a mounting device, said head maintenancearrangement having an ability to receive a drive head; and press fittingthe head maintenance arrangement to the mounting device free of staking.93. The method of claim 92, further comprising: removing the head fromthe head maintenance arrangement prior to said abutting.
 94. The methodof claim 92, wherein said head maintenance arrangement comprises a headassembly.
 95. The method of claim 92, further comprising providing themounting device with a bore passing therethrough prior to said abutting.96. The method of claim 95, further comprising aligning the headmaintenance arrangement with the mounting device.
 97. The method ofclaim 96, wherein the aligning comprises passing a first relativelynarrow device through the head maintenance device to relatively fix headmaintenance device position.
 98. The method of claim 97, wherein thealigning further comprises passing a second relatively narrow devicethrough the head maintenance device and the bore of the mounting deviceto align the head maintenance device with the mounting device.
 99. Themethod of claim 92, wherein said abutting comprises fixedly mounting themounting device to an assembly tool and locating said head maintenancedevice adjacent to the fixedly mounted mounting device.
 100. The methodof claim 99, wherein the press fitting comprises compressing theassembly tool, thereby pressing the head maintenance device against thefixedly mounted mounting device.
 101. The method of claim 99, whereinsaid assembly tool comprises a plurality of sections, and said sectionsemploy a compression device to draw said sections together and hold saidhead maintenance device and said fixedly mounted mounting device.
 102. Asystem for replacing a drive head in a media writer, comprising: anassembly tool having a plurality of component parts; a clamping devicefor receiving the assembly tool; a drive head maintenance apparatus formaintaining the drive head; and a mount; wherein the assembly tool hasthe ability to hold the drive head maintenance apparatus adjacent themount and the clamping device has the ability to compress the assemblytool, thereby press fitting the drive head maintenance apparatus to themount.
 103. The system of claim 102, further comprising at least onealignment pin for aligning the mount with the drive head maintenanceapparatus in connection with the assembly tool.
 104. The system of claim102, wherein said assembly tool further comprises at least onecompression device for applying pressure between the component parts tomaintain the mount and drive head maintenance apparatus.
 105. The systemof claim 103, wherein said mount comprises a bore, and at least onealignment pin passes through the drive head maintenance apparatus andthe bore in the mount.
 106. A drive head change apparatus, comprising: ahead assembly having the ability to support hardware comprising at leastone drive head; and a head mount tab for adjoining the head assembly topositioning hardware, wherein said head assembly is affixed to said headmount tab in a removable manner thereby minimizing potential damage tosaid mounting tab.
 107. The apparatus of claim 106, further comprisingat least one alignment pin for aligning the head mount tab with the headassembly prior to press fitting the head assembly to the head mount tab.108. The apparatus of claim 107, wherein said head mount tab comprises abore, and at least one alignment pin passes through the head assemblyand the bore in the head mount tab.
 109. The apparatus of claim 106,further comprising an assembly tool for holding the head mount tab. 110.The apparatus of claim 109, wherein the assembly tool has the ability tohold the head assembly adjacent the head mount tab.
 111. The apparatusof claim 110, further comprising a clamping device having the ability tocompress the assembly tool, thereby press fitting the head assembly tothe head mount device.
 112. The apparatus of claim 109, wherein saidassembly tool further comprises at least one compression device forapplying pressure between the component parts to maintain the mount anddrive head maintenance apparatus.
 113. A system for detecting movementof a plurality of disks mounted to a spindle, comprising: atransmitter/receiver capable of emitting a first beam of energy towardsaid spindle and receiving energy from said spindle; and an errorcalculator determining differences between actual head position based onsaid reflective element position and orientation of the spindle. 114.The system of claim 113, wherein said transmitter/receiver comprises aninterferometer, and said energy comprises light energy.
 115. The systemof claim 113, wherein the transmitter/receiver comprises a laser diodeand an optical detector.
 116. The system of claim 113, wherein thespindle is polished to provide a high degree of reflectivity.
 117. Thesystem of claim 113, wherein the spindle is at least partially coveredwith a reflective material.
 118. The system of claim 114, wherein theinterferometer comprises a dual beam interferometer, and thetransmitter/receiver further comprises a plurality of optical detectors.119. The system of claim 113, wherein the spindle has a circumferenceand where the spindle comprises elements regularly spaced around thecircumference of the spindle.
 120. The system of claim 113, furthercomprising a lensing arrangement for receiving light energy andconverting said received light energy into collimated light energy. 121.A system for positioning a head over a disk, said disk mounted to aspindle, comprising: a transmitter/receiver capable of emitting a firstbeam of energy toward said spindle and receiving energy from saidspindle; a reflective element positionally emulating the head andoriented to receive a second beam of light energy from saidtransmitter/receiver and reflect the second beam back toward saidtransmitter/receiver; and an error calculator determining differencesbetween actual head position based on said reflective element positionand orientation of the spindle.
 122. The system of claim 121, whereinsaid transmitter/receiver comprises an interferometer, and said energycomprises light energy.
 123. The system of claim 121, wherein thetransmitter/receiver comprises a laser diode and an optical detector.124. The system of claim 121, wherein the spindle is polished to providea high degree of reflectivity.
 125. The system of claim 121, wherein thespindle is at least partially covered with a reflective material. 126.The system of claim 122, wherein the interferometer comprises a dualbeam interferometer, and the transmitter/receiver further comprises aplurality of optical detectors.
 127. The system of claim 121, whereinthe spindle has a circumference and where the spindle comprises elementsregularly spaced around the circumference of the spindle.
 128. Thesystem of claim 121, further comprising a lensing arrangement forreceiving light energy and converting said received light energy intocollimated light energy.
 129. A method for positioning a head above adisk rotating about a spindle, comprising: transmitting a first lightenergy beam to said spindle and receiving light energy reflected off thespindle; transmitting a second light energy beam to a reflective elementpositioned to substantially emulate head position; receiving lightenergy from said transmitting that is reflected off the reflectedelement; computing an error signal based on positional differencesbetween said spindle, said emulated head, and disk orientation; andaltering head position based on the computed error signal.
 130. Themethod of claim 129, wherein the reflective element comprises a cornercube mounted to an e-block.
 131. The method of claim 129, wherein thefirst light energy transmitting beam and second light energytransmitting beam emanate from a dual beam interferometer.
 132. Themethod of claim 129, wherein the second light energy beam is collimated.133. The method of claim 129, further comprising transmitting a thirdlight energy beam to the disk to provide z-axis measurement and providetilt data.
 134. The method of claim 129, wherein orientation of thefirst light energy beam is approximately 90 degrees different fromorientation of the second light energy beam.
 135. The method of claim129, wherein orientation of the first light energy beam is greater thanapproximately 45 degrees from orientation of the second light energybeam.
 136. A system for accurately positioning a head over a media disk,said media disk rotating about a spindle, comprising: a dual beaminterferometer emitting a first beam of light energy toward said spindleand receiving reflected light energy from said spindle; a reflectiveelement positionally emulating the head and oriented to receive a secondbeam of light energy from said dual beam interferometer and reflect thesecond beam back toward said dual beam interferometer; an errorcalculator determining differences between actual head position based onsaid reflective element position and orientation of said spindle. 137.The system of claim 136, further comprising a lensing arrangement forreceiving light energy transmitted from the dual beam interferometer andconverting said light energy into collimated light energy.
 138. Thesystem of claim 136, wherein the reflective element comprises a cornercube mounted to an e-block.
 139. The system of claim 136, wherein thesecond light energy beam is collimated.
 140. The system of claim 136,further comprising transmitting a third light energy beam toward thespindle to provide z-axis measurement and provide tilt data.
 141. Amethod for efficiently positioning a head above a media disk rotatingabout a spindle, comprising: transmitting a first light energy beam tosaid spindle and receiving light energy reflected off the spindle;transmitting a second light energy beam to a reflective elementpositioned to substantially emulate head position and receiving lightenergy reflected off the reflective element; computing an error signalbased on positional differences between said spindle, said emulatedhead, and disk orientation; and altering head position based on thecomputed error signal.
 142. The method of claim 141, wherein thereflective element comprises a corner cube mounted to an e-block. 143.The method of claim 141, wherein the first light energy transmittingbeam and second light energy transmitting beam emanate from a dual beaminterferometer.
 144. The method of claim 141, wherein the second lightenergy beam is collimated.
 145. The method of claim 141, furthercomprising transmitting a third light energy beam to the disk to providez-axis measurement and provide tilt data.
 146. The method of claim 141,wherein orientation of the first light energy beam is approximately 90degrees different from orientation of the second light energy beam. 147.The method of claim 141, wherein orientation of the first light energybeam is greater than approximately 45 degrees from orientation of thesecond light energy beam.
 148. A system for accurately positioning ahead over rotating media, said rotating media able to spin about acenter axis, comprising: an interferometer having the ability to emitlight energy and measure an effective distance between said head andsaid spindle; and means for computing a correction factor to be appliedto said spindle to correct for any perceived distance errors related tosaid head measurement.
 149. A system for determining spindle orientationinaccuracies, comprising: an interferometer having the ability to emitlight energy and measure an effective distance between saidinterferometer and said spindle; and means for computing a correctionfactor for application to the spindle to correct for perceived errors.150. The system of claim 149, wherein the interferometer comprises a tricoupler.
 151. The system of claim 149, wherein the light energy emittedfrom the interferometer is collimated.
 152. The system of claim 149,further comprising transmitting an additional energy beam toward thespindle to ascertain z-axis performance and tilt data.
 153. The systemof claim 149, wherein orientation of the light energy is approximately90 degrees different from orientation of the additional light energybeam.
 154. The method of claim 149, wherein orientation of the lightenergy is greater than approximately 45 degrees from orientation of theadditional light energy beam.
 155. A method for minimizing media writingerrors in a computing device, comprising: writing a portion of a databurst on a first pass; and writing additional portions of the data burston subsequent passes.
 156. The method of claim 155, wherein the databurst comprises a number of dipulses, and wherein writing the portion ofthe data burst comprises writing one dipulse on the first pass and allremaining dipulses on the second pass.
 157. The method of claim 156,further comprising computing an energy value for multiple bursts writtenusing the multiple passes.
 158. The method of claim 157, furthercomprising evaluating the computed energy value and rewriting theportion and additional portions if the energy value exceeds apredetermined threshold.
 159. A method for increasing magnetic diskyield during the manufacturing process, comprising: initially writing afirst complete set of servo data to a magnetic disk; subsequentlywriting at least one additional set of servo data to the magnetic disk;evaluating the quality of the servo data written; and removing thelowest quality servo data and retaining the highest quality servo data.160. The method of claim 159, wherein said initially writing and saidsubsequently writing comprises writing the first complete set and the atleast one additional set to a substantially identical region on themagnetic disk.
 161. The method of claim 159, wherein the evaluatingcomprises averaging the qualities of servo data written.
 162. The methodof claim 159, further comprising assessing head quality based on saidevaluating.
 163. The method of claim 162, further comprising removingheads of inferior quality indicated by said evaluating and saidassessing.
 164. The method of claim 159, wherein said initially writingcomprises: partitioning the first set of servo data into multipleoverlapping contiguous segments and a first predetermined quantity ofthe overlapping contiguous segments are written during a first pass.165. The method of claim 164, wherein the subsequently writing compriseswriting a second predetermined quantity of the overlapping contiguoussegments to the disk.
 166. The method of claim 159, wherein saidevaluating comprises determining energy perceived by reading the firstcomplete set and the additional set of servo data.
 167. The method ofclaim 166, wherein the energy comprises a difference between the firstcomplete set of servo data and one additional set of servo data dividedby the sum of the first complete set of servo data and the oneadditional set of servo data.
 168. The method of claim 166, whereininitial and subsequent writing is determined unsatisfactory if theenergy exceeds a predetermined threshold.
 169. A method of writing to adisk, comprising: writing data to the disk; rewriting said data to thedisk at locations offset from data previously written to the disk; andremoving data having lowest quality from the disk.
 170. The method ofclaim 169, wherein the data comprises servo data.
 171. The method ofclaim 170, wherein the servo data comprises one set of servo data and atleast one additional set of servo data.
 172. The method of claim 171,wherein said writing and said rewriting comprise writing the firstcomplete set and the at least one additional set to a substantiallyidentical region on the magnetic disk.
 173. The method of claim 170,further comprising evaluating quality of servo data written to the disk.174. The method of claim 173, further comprising assessing head qualitybased on said evaluating.
 175. The method of claim 174, furthercomprising removing heads of inferior quality indicated by saidevaluating and said assessing.
 176. The method of claim 170, whereinsaid writing comprises: partitioning the first set of servo data intomultiple overlapping contiguous segments and a first predeterminedquantity of the overlapping contiguous segments are written during afirst pass.
 177. The method of claim 176, wherein the rewritingcomprises writing a second predetermined quantity of the overlappingcontiguous segments to the disk.
 178. The method of claim 173, whereinsaid evaluating comprises determining energy perceived by reading thefirst complete set and the additional set of servo data.
 179. The methodof claim 178, wherein the energy comprises a difference between thefirst complete set of servo data and one additional set of servo datadivided by the sum of the first complete set of servo data and the oneadditional set of servo data.
 180. The method of claim 178, whereininitial and subsequent writing is determined unsatisfactory if theenergy exceeds a predetermined threshold.
 181. A servo data writingapparatus, comprising: means for writing data to a disk; means forrewriting said data to the disk at locations offset from data previouslywritten to the disk; and means for removing data having lowest qualityfrom the disk.
 182. The apparatus of claim 181, wherein the datacomprises one set of data and at least one additional set of data. 183.The apparatus of claim 182, wherein said writing and said rewritingcomprise writing the first complete set and the at least one additionalset to a substantially identical region on the disk.
 184. The apparatusof claim 182, wherein said writing and said rewriting comprise writingthe first complete set and the at least one additional set tosubstantially different regions on the disk.
 185. The apparatus of claim181, further comprising means for evaluating quality of data written tothe disk, said evaluating means providing an evaluation to said removingmeans.
 186. The apparatus of claim 185, wherein said evaluating meansdetermines energy perceived by reading the first complete set and theadditional set of data.
 187. The apparatus of claim 186, wherein saidevaluating means determines writing and rewriting is unsatisfactory ifthe energy exceeds a predetermined threshold.
 188. A method of assessingtrack writing performance on a media, comprising: monitoring spindleaxis position with respect to a reference position; and providing saidspindle axis position with respect to a reference position to aprocessor.
 189. The method of claim 188, wherein said monitoringcomprises evaluating spindle axis position using a sensing device. 190.The method of claim 189, wherein the sensing device comprises aninterferometer.
 191. The method of claim 190, wherein the interferometercomprises a differential interferometer.
 192. The method of claim 188,wherein said monitoring comprises evaluating spindle axis position usinga capacitance probe.
 193. The method of claim 188, wherein themonitoring comprises evaluating spindle axis position using an inductivesensor.
 194. The method of claim 188, wherein the monitoring comprisesevaluating spindle axis position using an alternate position opticalsensor.
 195. A method of computing a media track writing performancemetric, comprising at least one from the group including: computing astandard deviation of an observed track write radius from a desiredtrack write radius and decomposing the standard deviation intorepeatable and nonrepeatable components; computing time dependent servomark positions; and computing optically inferred spindle axis positions.196. A method of computing a performance metric for media track writing,comprising: monitoring position of a rotating component of a holdermaintaining said media; computing a topological radius of a surface ofsaid rotating component; and determining a difference between therotating component position and the topological radius, wherein saiddifference equals rotating component wobble.
 197. The method of claim196, further comprising separating wobble into a repeatable part and anonrepeatable part.
 198. The method of claim 197, wherein thenonrepeatable part comprises nonharmonic components.
 199. The method ofclaim 197, wherein the repeatable part comprises harmonics of arotational rate of said rotating component.
 200. A method for biasing atleast one disk fixedly attached to a spindle, comprising: applying abiasing lateral force to a first disk fixedly attached to said spindlethereby tightly interfacing said disk with the spindle at one portion ofthe disk; and applying a differently oriented biasing lateral force toany second disk fixedly attached to said spindle.
 201. A method forbiasing a disk attached to a spindle, comprising: applying a biasinglateral force to the disk fixedly attached to said spindle therebytightly interfacing said disk with the spindle at one portion of thedisk.
 202. A system for maintaining media, comprising: a cap; at leastone spring holding the cap; and a fluid release ball bearing arrangementhaving the ability to slidably engage and release said cap using forcegenerated by the at least one spring.
 203. A device for maintainingmedia, comprising: a fluid release arrangement having the ability toslidably engage and release a cover.
 204. A device for holding arotating hub, comprising: a chuck clamp housing; a mounting platefixedly mounted to the chuck clamp housing; a spindle within the chuckmounting plate; a chuck clamp surrounding the chuck mounting plate andhaving the ability to engage the hub, wherein said chuck clamp comprisesa plurality of finger elements.
 205. The device of claim 204, furthercomprising a Belleville spring and a fluid release system providing theability to attach and release said device and said hub.